I would love to see more of Cad Bane's crew from the Hostage Crisis episode added to the game, but mainly:
Robonino - he could be really fun with a stun baton, though they would probably give him explosives (ugh) as a secondary
Maybe add the rest of the crew too, but don't really care about them as much:
Aurra Sing
Shahan Alama
HELIOS-3D (could do without him though since he'd be so similar to the current IG droids)
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