I am hoping that this is subterfuge. Like they know that they can't hide RDJ if he came back to the MCU so they say he is going to come back as Doom, when he is going to return as Ironman.
I really like your idea too. That it is for hype, but it'll be a cameo.I stand by my earlier speculation that, given they came on stage with over dozen OTHER people wearing Doom costumes…RDJ is just playing one of SEVERAL versions of Dr Doom that will be featured in the film. With Deadpool and Wolverine, and even Flash, audiences seem fine with multiple actors playing different “flavors” of a character.
You put Victor von Doom in Tony Stark's body in a comic and it is something to tell a story about. Even there, I admit, it sounds like a dumb idea to me. But it would exist simply to be explored.
You put Victor von Doom in Tony Stark's body in a movie and virtually nobody believes it wasn't just because you wanted to cash in on Robert Downey, Jr. I wouldn't even believe it and I already found out that it would have a basis in the comics.
Now...that might be all there is to. Maybe they just wanted to cash in on Robert Downey, Jr. But I really hope not. If they want my idea, The Fantastic Four have been rumored to have been active in the 60s or 70s when the old Antman was and will somehow be dumped into our time. Maybe all of that is malarky, but I didn't make it up. If they do that, then they have have a quick exposition to say that they finally defeated Dr Doom back in the 70s and he died. Then in the post credits, you reveal that in an alternate timeline, Tony Stark became Dr Doom and for some reason he comes to ours. To me, that is an idea that can be explored. What if Tony Stark had been evil, but just as intelligent and wealthy and resourceful? It might be a little unfair to the character of Dr Doom, but you can give him an awful lot of the character. Besides...I mean they gave us a totally fake Mandarin and were sincere about it but when they found out how upset people were they created an elaborate story to show us how that fake Mandarin wasn't the real Mandarin and then gave us...another more interesting character that was also really an entirely new Mandarin. But I thought he was interesting.
I was all in on seeing Majors play several more different characters and I'm disappointed that he wasn't the man they needed to do the job. But there is a recasting trick that gets done ALL the TIME, but only in a limited scenario where it works and they happen to fit that scenario. They actually did it on Loki Season 2 WHILE everyone was trying to figure out if they could recast him. Nasri Thompson already played him on two episodes and no one even thinks about it because obviously you have to recast when the character is going to be 30 years younger. So don't cast someone that looks and sounds kinda like him that is his age. Cast someone 20 years younger or older. TV and movies have already taught us to accept that someone will be recognized across a crowded room by another character who hasn't seen them for 20 years when they looked like a totally different actor. Post credit scene aside, Kang doesn't need to be the same age as He Who Remains.They could have just recast Kang but now were going for this desperation play instead. I guess we will see if they can manage to pull a miracle out of their hat. Given a lot of the recent stuff however...