When i first watched IM3, i assumed(Rightly or wrongly), that Extremis cannot be removed from people. That once they had it, they had it for good.
And that Tony's line of "As promised, i got Pepper Sorted out. Took some tinkering, but then i thought to myself: Why stop there?"
I was thinking: "What if Tony perfected Extremis?"
I know that's obvious, but what i mean is: "What if Tony perfected it to the extent that Pepper *still* has Extremis in her. But she can live with it because Tony made it non-volatile?"
If that's the case, Tony could have imbued himself with Extremis, and could also have suits powered by the extremis energy.
It's too close to the Fantastic 4 to have Tony producing flames from his feet and flying around like the Human Torch, but a suit that can convert Extremis isn't too much of a stretch.
Of course, if Tony doesn't have Extremis, it's no stretch at all to have him simply without a reactor, but with more suits that DO have reactors.