Disney cannot use Marvel east of the Mississippi, which eliminates WDW. They cannot use any characters currently represented in IOA, nor can they use any character which is within the "family" of those characters.
Look, all Disney needs to do is put some money into digging a "canal" to divert the Mississippi to run through Wedgefield, FL.
Then BAM! WDW is west of the Mississippi. No more problem.
Marvel can replace all the WDW attractions with no legal worries. I would start by renaming Cinderalla Castle as Stark Castle. We'd have the Hulk's Be Our Guest Restaurant and Professor Xavier's X-Men Mansion. All WDW's problems would be solved, and all they have to do, if my historical research is correct, is hire 45,000 Panamanians and just hope that malaria isn't as big of a problem in the eastern USA.