Perhaps instead of one world, it could be a multi-level world, with all the various facets of the Marvel Universe on display; level one could be Manhattan and feature Spider-Man as your partner. Level/visit 2 could take place in Wakanda or Asgard and feature the Avengers as your teammates. Level/visit 3 could take place in space with the Guardians of the Galaxy or the Fantastic Four as your partners. Just a thought.