I think there should be no more than two new units to each faction. Having a billion different options isn't necessary.
I'd add-
Republic:
-
Advanced Recon Commando (ARC)
CIS:
-
Octuptarra Combat tri-droid
Empire:
-
Storm Commando
Rebels:
-
Rebel Infiltrator
That would be completely awesome! Those units would make a fine addition to the game. I'd also like to see some more heroes/villains added.