Well, Batman and Lex Luthor would probably lose their "Smartest Men on Earth" title when they have to co-exist with Reed Richards, Dr Doom, Hank Pym, Tony Stark, Bruce Banner, T'Challa, etc.
In fact, I'd like to see Lex Luthor and Dr Doom as arch-rivals.
I'd think Batman would be the one trying to neutralize Stark Industries TBH. He wouldn't like the idea of a loose cannon like Stark producing weapons like the Iron Man suit for anyone. But then after the Obadiah Stane thing he realizes Tony is the better one in charge and lays off.