The suggestions I have seen always seem very extreme and simplistic or they are just oddball way just to fix the problem not caring about other ramification. But I have seen some very unique and great ideas on how to fix these problems.
I for one want to have a game where it feels like there are armies clashing on a real battlefield but the current game provides little benefit for high-ground advantage and forces an easy natural and a close 3rd and with the dramatically large maps a player with sub-par macro finds themselves at a great disadvantage to a protoss with average macro and a proxy pylon. While a protoss player has no real map control and must either all-in/timing attack or turtle to T3.
I will address each issue one at a time
High-ground advantage
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I have seen many people suggest going back to %miss/reduced damage or -1 range for low-ground but i find this to be rather harsh and uncomfortable.
A zerg player who already has himself at a disadvantage in range would be effected much more then a terran or protoss player and would remain at a disadvantage when defending high ground
I would like to see +1/2 range to high-ground -1/2 range low-ground this may not seem like a significant change but it would mean you could deal more damage then normal from the high-ground and low-ground would still be pulled in closer but since more of your units would now be able to cover more area moving next to cliffs without vision would now be much more risky as well siege tanks and colossus would be more effective on cliffs making positioning more important and making hydralisks a rather scary defender.
A zerg player who already has himself at a disadvantage in range would be effected much more then a terran or protoss player and would remain at a disadvantage when defending high ground
I would like to see +1/2 range to high-ground -1/2 range low-ground this may not seem like a significant change but it would mean you could deal more damage then normal from the high-ground and low-ground would still be pulled in closer but since more of your units would now be able to cover more area moving next to cliffs without vision would now be much more risky as well siege tanks and colossus would be more effective on cliffs making positioning more important and making hydralisks a rather scary defender.
Warp gates
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This is a long one.
I would like to see a fundamental change in warpgate with the addition of a warp web every warpgate, nexus and a new structure the bridge(I will adress this in a moment) generate a field akin to the power field. Warpgates could then only warp in on a space with a warp web and power that is connected to its web. This means if a protoss wants to create a proxy pylon he has to connect the warp web to that powerfield. Now keep in mind a nexus would have a rather large warp web as would the warpgate say 11-15. Now back to the idea of the bridge these would create connections between webs over great distance any two can be attuned and this can be changed as the game progresses these would be high value targets in any protoss base that would cut off warpins in that base or at that proxy pylon meaning more investment for defenders advantage anywhere. As well the warpprism would have a new role because it would act as a bridge so by bringing a prism around you could turn any pylon into a reinforcement hub. These changes make the protoss have to invest more and add incentives to take map control.
With these changes to warpgates I would see gateway be changed so that it is either removed from the game or produces units more quickly then the waprgate but as it stands there is no choice and it needs to be changed.
These changes make it possible to introduce new gateway units with more rolls without throwing the game way out of balance, and opens up new roles for protoss units while eliminating super early 4 gate and allowing for more interesting strategic plays.
PS I would see protoss units get minor changes not exactly buffs with this alteration think +10 shields on zealot and stalkers do bonus to light not armored
I would like to see a fundamental change in warpgate with the addition of a warp web every warpgate, nexus and a new structure the bridge(I will adress this in a moment) generate a field akin to the power field. Warpgates could then only warp in on a space with a warp web and power that is connected to its web. This means if a protoss wants to create a proxy pylon he has to connect the warp web to that powerfield. Now keep in mind a nexus would have a rather large warp web as would the warpgate say 11-15. Now back to the idea of the bridge these would create connections between webs over great distance any two can be attuned and this can be changed as the game progresses these would be high value targets in any protoss base that would cut off warpins in that base or at that proxy pylon meaning more investment for defenders advantage anywhere. As well the warpprism would have a new role because it would act as a bridge so by bringing a prism around you could turn any pylon into a reinforcement hub. These changes make the protoss have to invest more and add incentives to take map control.
With these changes to warpgates I would see gateway be changed so that it is either removed from the game or produces units more quickly then the waprgate but as it stands there is no choice and it needs to be changed.
These changes make it possible to introduce new gateway units with more rolls without throwing the game way out of balance, and opens up new roles for protoss units while eliminating super early 4 gate and allowing for more interesting strategic plays.
PS I would see protoss units get minor changes not exactly buffs with this alteration think +10 shields on zealot and stalkers do bonus to light not armored
Force Field
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I would see a minor reduction for the cost of FF
Give it reduced range to about 6 and tether it to the sentry at about 9 range
These changes make FF a harder to use aggressive tool so spiting armies will be much less common allowing for overall buffs to protoss gateway armies
It will be over all better defensively so one sentry can hold a flank for a short time
Another (More extreme but my favorite idea)
Give everyone a T2-2.5 massive unit
This dose several things
It makes armies smaller (Massive units cost alot)
It gives zerg a better answer to FF
Leaves FF as an aggrasive option
Makes Tempest more viable (more stuff to shoot)
Gives everyone a big new unit to trample down FF benefiting good army positioning
Fungals
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While I personally don't mind fungals I see the problem others have with it.
My solution is rather different from any that I have seen.
Make the root an upgrade.
but beyond that I would
I would give marines an upgrade that reduces spell damage against them marginally with the upgrade it would take 3 fungals to kill a marine (would also help against storm but rather insignificantly). I see the root as being the focus of fungal so I would prefer it if it could stay and while fungals are also good against air I believe it is their best counter to mass air.
Make it so that fungal allows for ability use, stalkers can blink out, zealots can charge out it wouldn't prevent damage but it could prevent the root witch in the end is the main problem (this could also help marines) Could make stim remove the root effect at the end of its duration (for cool micro techniques)
My solution is rather different from any that I have seen.
Make the root an upgrade.
but beyond that I would
I would give marines an upgrade that reduces spell damage against them marginally with the upgrade it would take 3 fungals to kill a marine (would also help against storm but rather insignificantly). I see the root as being the focus of fungal so I would prefer it if it could stay and while fungals are also good against air I believe it is their best counter to mass air.
Make it so that fungal allows for ability use, stalkers can blink out, zealots can charge out it wouldn't prevent damage but it could prevent the root witch in the end is the main problem (this could also help marines) Could make stim remove the root effect at the end of its duration (for cool micro techniques)
Deathball
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I would add a new unit concept.
Raiders, a raiding unit receives bonuses to killing structures so it targets tech, production, undefended expands. This it a unit that would be designed to work better in small groups not massed it would be lousy unit to unit but against small defense teams and defensive structures it would tend to win out.
This alters the base race dynamic if you have a big slow army you cant move out with everything or your base will be torn apart because raiders trade better in a base race. This forces people to rethink mine and burn bases or leaving their base undefended because raiding units would allow for favorable base trading even against a larger force meaning you can have an army at base defending against a deathball while you wreck their base though it would lose out in larger engagements, in small unit to unit brawls they would shine with higher front on damage or unique abilities.
This means one photon cannon buys you maybe 6 seconds or less while 2 siege tanks might repel the attack.
Raiders, a raiding unit receives bonuses to killing structures so it targets tech, production, undefended expands. This it a unit that would be designed to work better in small groups not massed it would be lousy unit to unit but against small defense teams and defensive structures it would tend to win out.
This alters the base race dynamic if you have a big slow army you cant move out with everything or your base will be torn apart because raiders trade better in a base race. This forces people to rethink mine and burn bases or leaving their base undefended because raiding units would allow for favorable base trading even against a larger force meaning you can have an army at base defending against a deathball while you wreck their base though it would lose out in larger engagements, in small unit to unit brawls they would shine with higher front on damage or unique abilities.
This means one photon cannon buys you maybe 6 seconds or less while 2 siege tanks might repel the attack.
Protoss Area control
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The protoss need an area control unit there is no question one of the great contributors to the T3 deathball and all-in attacks is the lack of good map control units. For protoss I do not think they need more damage or something that can super charge their deathball so you have to be careful.
The solution I have come up with is a "shield drone" Probably produced from the robo it would have heavy shielding and no attack it could deploy creating a shielded area where its shields take the damage before the rest of the protoss forces
This would create many unique and interesting strategies for the protoss player such as setting them up to protect buildings, probes that are being harassed, or just outside of a siege line to buffer your zealots as they approach the enemy. I feel a unit like this could not only make air play and map control plausible I think it would make protoss feel all around more Protossy with the added durability but without good placement and consideration this unit would add little to your army
The solution I have come up with is a "shield drone" Probably produced from the robo it would have heavy shielding and no attack it could deploy creating a shielded area where its shields take the damage before the rest of the protoss forces
This would create many unique and interesting strategies for the protoss player such as setting them up to protect buildings, probes that are being harassed, or just outside of a siege line to buffer your zealots as they approach the enemy. I feel a unit like this could not only make air play and map control plausible I think it would make protoss feel all around more Protossy with the added durability but without good placement and consideration this unit would add little to your army
Skyterran
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I just really want to see this it makes me all giddy but to have this they need a real gunship not some fragile little thing like the banshee something that can go out and fight and trade well in a real fight.
Zerg Swarm Host
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I love the concept of the unit but it feels to potent and to slow I would love if it spawned faster but made them weaker to create more of a continual tide of units not tower defense waves so along with extended life i want faster spawn rate but make them weaker that way it feels more zergy and you make them feel more pressure because the longer they wait to deal with it the more build up.
Zerg Corruptor
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They just do nothing for me boring over all I would love it if they had an ability that was either more active or more exciting but I have no clue Please give me some ideas.
Please Post your thoughts on my ideas and what you think!

Feedback is greatly appreciated :D sorry it was so long.