In my opinion the best solution for the warpgate would be to switch the building times of gateway and warpgate, like it was said in posts before.So that the warpgates take longer to warp in then the gateways to build an unit. I think the developer took the idea of warping in units a little bit too far,because the don't realized that warping in units on nearly every point on the map, is an powerful ability on its own and that adding also the benefit of shorter buildtimes than the gateway has causes balancing issues.
Switching buildtimes between warpgate and gateway has the following benefits:
1. It would add an strategic reason for transforming an warpgate back into an gateway. This would lead to an deeper gameplaymechanic, where the players must figure out at which time is it good to have which amount of gateways and which amount of warpgates. And so the gateways would become useful in the lategame.
2.Early units could be made a bit stronger, because of the cooldown nerf and so toss would feel more powerful in the earlygame.
The Downside would be, that their would be no more intense timing-pushes where you try to hold on against an pushing toss and even if you kill his units he is warping in again and again.
So even better is the idea of giving warpgates energy instead of cooldown , in an way like the nexus has it for chronoboost or the commandcenter has it for mules.You could balance the energy which is needed for one warpin so, that the time between warpins would take longer then the gateway needs to build.This would have following
additional benefits:
In combination with an alter version of the mothershipcore´s abillity energize , could it be possible, in my opinion, to balance warping in bigger units like the colossus or immortal.
This would work as follow:
The gateway could save up a max of 200 energy. Zealot and stalker coast each 200 energy to warp in but , and this would be the important point, i would give the mothershipcore the ability to suck up 800 energy max with the reinvented ability energize, similar to the viper sucking up energy, only with the difference that the mothershipcore would not damage the building but rater transports the energy from the building to itself and from their, if the player wants, to another building or unit , which can save energy. So that the new energize works in both directions , suck up energy and save it on the mothershipcore and the other direction would be to give an unit/building energy form the mothersipcore.
And if the mothershipcore sucks 4 warpgates dry and gets up to 800 energy it could generate an stationary field and warp in 2 Immortals or 2 Colossi for the warpin-coast of 400 for each warping in an unit out of the robotic facility.