Oh come on, if you had the option to go out in a blaze of glory, and then come back as a villain - BECAUSE YOU COULD - you'd do it... I would.
What's to say that I wouldn't have started out as the villain?! There is no escape from Chaos, it marks us all.
All I ask is that if, and I stress IF, he is actually going to play Dr. Doom then please be Dr. Doom and not some stupid version of Tony Stark who just acts like Doom from another multiverse.
I'd be surprised if they didn't somehow... someway... try to shoehorn him back into a Tony Stark role.