And how about for ground units:
Imperial:
Stormtrooper (2,2,1), Snowtrooper (3,1,1), sandtrooper (1,3,1), scout trooper (2,1,3) and royal guard (3,4,1) and darktrooper (4,3,1)
Rebels:
Fleet Trooper (2,2,1), Rebel Commando [endor] (3,1,1) Hoth Trooper (1,3,3), Swoop trooper (2,1,2) and wookie (4,3,1) and mon cal trooper (3,4,1)
Republic
Clone Trooper (2,2,1), ARC Trooper (3,1,1), Heavy Clone Trooper (1,3,1), Speederbike Clone (1,3,3), Jedi Knight (4,4,1) [find some way to limit jedi knights]
Confederacy
Battle Droid (2,2,1), Super Battledroid (3,1,1), Droideka [destroyer droid] (1,3,1), STAP (2,1,3), Advanced Droideka (3,4,1), Advanced Super Battledroid (3,4,1).
Heavy Ground Units. Cannot capture cities (so troopers arent made redundant)
Empire: AT-ST (6,4,2), AT-AT (7,7,1).
Alliance: AT-PT (4,3,2), Captured AT-ST (6,4,2).
Confederacy: AAT (6,4,2), MTT (4,5,2;transports 3), Hailfire Droid (7,4,2) and Spider Droid (6,6,2)
Republic: AT-PT (4,3,2), SPHA-T (7,4,2), AT-TE (6,6,2)
Any good? I know each side do not have the same amount of vehicles, but it occurs to me that where the empire have AT-ATs, the alliance would tend to rely on snowspeeders, and where the confederacy has MTTs, the Republic would use their gunships. The troopers dont upgrade, as this leaves more variation in the ground forces - the empire for instance use stormtroopers in the same squad as they would use royal guard - i recommend making the stronger troopers (royal guard, wookies, jedi, etc) much more expensive, and prevent other troopers being upgraded.