I'd like to see many of the EU characters in any multiplayer mode - particularly from the later eras, like Roan Fel and the Imperial Knights, or Darth Krayt and Darth Talon.
I think a multiplayer, whether online or regular single console multiplayer, would be a welcome addition to the next-gen version. Given the backlash over the complete lack of one, I think the developers would be foolish to neglect to add one next time out.
Mara Jade might be a good candidate for a character in a sequel - though as said, not a main one. Mainly because she has a storyline already. I'd prefer a totally original one.