So, back to the topic of the news from Comic Con ... RDJ as Victor Von Doom is actually a great casting choice on paper. Because he has spent so much time as Iron Man, people forget what a talented and versatile actor he actually is.
This casting choice is soiled because RDJ is Iron Man. Had he never been Iron Man, then I think this casting choice would receive unanimous excitement ... Or would it? RDJ as Iron Man basically created the MCU, and it was RDJ's comeback role after a decade or so of his very public substance abuse issues. So ... Yeah, I don't know how you can cast him as another MCU character. It's a bizarre choice that reeks of desperation.
The only way they can make this work, IMO, is to completely make Doom all CGI and have RDJ provide just voicework that doesn't sound like him at all.