Gunship/Jedi Starfighter: Well I'll change the Jedi Starfighter to be the main Anti-Air unit. I've already said the gunship has a long reload time, and it will turn out quite like the US Camanche in CC Generals, which I think works in that game and isn't overpowered. The main differences between the Gunship and the Comanche are that the Gunship can transport 8 pop worth of infantry and doesn't have the Comanche's rocket barrage special ability. The Gunship is also less well armoured with less Hit Points. I strongly believe this will work. I should also note for the purposes of gameplay the Gunship won't attack with all five lasers, that would be way too overpowered.
Diplomat: You may have missed the fact that the Diplomat doesn't walk between Trade Points, it stays at the ally's one permanently. The best thing to do is ly him in on a Gunship or walk him in inside an AT-TE.
Forward building: Well you're right about the forward building. I'll make it that you can only move buildings to within a radius of a Forward Command Center. This will limit the Republic's forward Building a bit but still make them quite good at it (as they should be).