It was my understanding that Disney can't use any performing character Universal has used. Meaning, they have costumes for Hulk and IronMan, despite being hardly used, Cap, Spidey, Rogue, Storm, Wolvie, Cyclopes, etc. But Stark isn't out as a character so he is game. Again, I don't know the details so I could be off base, but what I've always heard is that Disney was restricted to using costumed character based off Universal's scraps.