I wonder if, between this and the supposed involvement of the Mandarin and his nigh-mystical alien magic, is it too much compared to what's happened so far?
Why are people still worried about magic possibly being in IM3? Iron Man was just in a movie with freaking THOR and LOKI. I think people will believe anything now.
I don't know much about Extremis, but it does sound kind of weird. I'll say they should keep it simple and just let the armor stay as something that can only be put on.