I'm wondering which heroic characters you'd like to see facing a threat that's out of their comfort zone? And who would you like to see them up against?
For example, you might want to see the Ghostbusters trapped on a spaceship with a hive of Xenomorphs. Maybe you'd like to see the Men in Black going up against the First Evil from the Buffyverse. Perhaps you'd enjoy seeing the protagonists from The Walking Dead on board the Event Horizon.
Go for it!