I haven't worked out the special cards yet, but here are my ideas for bringing the number of "main" characters to 20, while also adding some humor.
1) Lando, C3PO, R2D2. Lando's power could be his money, C3PO could have cards like "Annoy" or "Won't shut up". He's be a good distraction character. R2 could have some neat abilities with mechanical things, ie; shutting down weapons/driods, etc.
2) Jabba the Hutt + 2 Gommorean Guards.(The green pig guys) Jabba could have some neat abilities with his access to the Rancor and Sarlac (sp?) pits. He'd have a ton of health too.
3) FOUR Ewoks! That's right! Weak individually but lethal en masse. Slippery fellows too.
4) FOUR Jawas! ME WANT JAWAS! They're so cute! Seriously though, you get enough of them together and you have your hands full.
5) Qai-gon Jin (sp) + Captain Tanaka (Amidala's Chief of Security). Jedi Powers + Range. 'Nuff said.
6) Gungans. Why not? They had a "grand army". Have the team of the King (whose name escapes me), the General, and Jar-Jar with some silly powers thrown in to the mix.
7) IG-88, Bossk, and another bounty hunter of your choice. Give those pesky Jedi three at once and see how they like it!
8) Grand Moff Tarkin, General Tagge, Admiral Motti. Have the 3 highest ranking Imperial Officers in Star Wars brandish a weapon and see how they fare.
So whatcha think? Can you think of any other neat combos to put in an expansion? If we make a big enough stink, maybe they'll finally make an official expansion for this great game. And while they're at it, they can fix Vader, Luke, ..........