That's why I specifically listed Guardians and Ant Man.
You wouldn't want to have a specific Marvel area (since the Avengers are tied to the Uni contract), but the character that aren't tied into that deal would work perfectly if they were mixed with other Disney "Heroes."
As for Star Wars, until the big SW expansion is done, I see a need for keeping most of the characters for Star Wars Weekends. But, having a couple of characters (like your idea of the Rebels characters) as part of this "Heroes" meet and greet area would fit perfectly.