Exterminator sounds op as hell , either its aoe ability would suck and thus be pointless or it would be op effectively being a strong meele tank unit that can also restrict the map and do aoe. Too similar to the herc.
Guardian sounds tailored for all ins and abusive plays, are we seriously thinking sentry drop into ´FFing off the main being the kind of gameplay we want to see over and over. Finding which spots on which maps can be abused and then see it abused over and over, we've seen that before and it was not fun or entertaining. Not to play and not to watch. Abusive and lacks counterplay, T is already sick cost efficient having manual forcefields to boot just sounds too much.
Jackal, yeah because more spellcasters is what we need for terran. Ghost and Ravens already fill that role and are used rarely, increase bio viability late game also seems needless. Bio is insane early-mid game and works fine late game(maybe not against P but then they do have ghosts or vikings to supplement).
Javelin, among tanks, mines, homing missiles and nukes you want to add more aoe explosives?
Unnamed unit, I suppose it might be the best base idea of the bunch but I still thinks its very bad. There's a reason blizz hasn't made any hardcounters in the game, at least not any that doesn't require upgrades and micro. Aoe against air with range like that is just silly, it would make all kinds of mass air play unviable vs terran as soon as they are able to get 3-4 of these babies up. Not to mention T is a ranged based race and has tons of tools to protect their air units against spread out enemy air. Its a hard counter with no way to counterplay it which makes it a very bad idea.
Why are all the ideas picked either things that already exists, roles that are filled or increadibly op. I would like to see a new terran unit that is not just a gimmick but could actually get used as a combat unit in a standrad army as an option besides the marine->bio and the helions>mech.