Gunship - Okay, I'll make the carry capacity 8. Any less and it gets unrealistic.
As for it being strong against Air, this is intentional. You may notice that the Republic has no ground-based Anti-Air unlike most civs. This means the Gunship is the only unit that can take out Aircraft well. It is less well armoured and has fewer hit points than most Aircraft, plus it is very expensive and will cost more Population, so I think in the end it all balances out. I should add that although the rockets are good against Aircraft, they have quite a long reload time, during which the Gunship is very vulnerable.
I think my Gunship is balanced. Whereas Windu's not only had powerful weapons and a transport ability but was also shielded, well armoured and fast, mine is not. My weapons are indeed powerful, yet the Gunship is unshielded, has few Hit Points, and is the second slowest Aircraft (not including Transports) after the Gungan one. I shall edit the document to make these points clearer.
Sniper - An ion rifle trooper would be good against Mechs, right? I wanted to leave that for the Clone Bikers. There is a bit of footage that was cut from the final film where you see a few Clones on Speederbikes zooming under the legs of Homing Spider Droids. They throw grenades at it, destroying it. I thought this looked so cool I wanted to include it. As for the Naboo and Rebels, there is no reason they can't have a sniper as well. Give me some more reasons to change it and I might consider.
Dropship - As described in the Transports
description, it means 10 population worth of mechs.