5. Don't Hurry To Introduce Dr. Doom
While I don't really consider Dr. Doom to have ever appeared in a live action theatrical movie (the guy who played the villain in the two previous flicks is really just a poor man's Norman Osborn with 2nd hand knock offs of the powers possessed by Colossus and Electro) imdb and other sources disagree with me. With this in mind, it's a rather obvious page from the superhero reboot playbook to skip the lead villain from the first movie anyway, but more importantly the core team needs as much time devoted to developing their character arcs and motivations on screen without having the plot intensive heavy weight that is doom taking up too much precious screen time. Dr. Doom works best as a character that comes boiling out of the cauldron that is Reed's past, than as someone introduced to the audience along with Johnny, Sue and Ben. He's got a rich back story that is worthy of a film that doesn't have to worry about telling the audience who the team is and how they're different from the previous team. More importantly, there are a lot of villains that are waiting on the bench to be used in an FF movie, so while Trank should lead with a strong foot, there should be something better set up for the sequel. Guys like the Mole Man, The Trapster, Fin Fang Foom and the Puppet Master are all worthy starter villains. It'd be fine to drop some hints here and there about the eventual coming of Doom, and a post credit scene is always a good place to set up the next villain, but Doom is definitely a "2nd movie's villain is waaay more vicious" type a guy. Speaking of viciousness...