[DraXXXen]

I think it would be hard to avoid using any armored villain in the sequals, so the best way to go about it is use the villains in a new way. Specifically have a handful of costumed villains on screen hired by another corporation to take down Stark/Ironman. This way you spend the movie developing the main corporate villains character (Justin Hammer perhaps) but use a fist full of foes like Spymaster, Ghost, Blizzard, Beetle, etc for action scenes. There is no rule saying Iron Man as to fight the actual mastermind behind it all, just his minions would be fine.