Just my personal opinon.
Speaking of Bob, I never quite understood that one episode where Bob had changed and didn't want to kill Bart, saved Bart's life from his brother and then several episodes later, with no explaination whatsoever, went back to his "kill Bart" phase and has been ever since.
Actually, I thought The Simpsons Movie was a bit of a disappointment. Definitely better than any episode of the show in years, but not what i'd want from a Simpsons feature film. Hardly any Mr. Burns (we didn't even see Homer sleeping at work, or Bart annoying Mrs Krabapell at school! What!?) The dome thing was dumb, and so was the villain.
For a Simpsons movie sequel, we need more of the Nuclear Power Plant, Mr Burns and Smithers, Springfield Elementary and Principal Skinner. I don't want Bob as the villain because it's way overdone. I'd like him to have some role in the film, though. He's too great a character not to use.