I believe that's what the 5E Champions Battlegrounds book was intended to present -- a group of adventures which could be run separately, but which also had an overarching plot to tie them together if a GM wanted it.
Rather than the 4E and earlier adventures, it would probably be easier to update the Champions adventures presented in Digital Hero to 6E, and collect the majority of them (there were fourteen in total) into a single volume. They have the advantage of being ready to run, already having written up NPCs, and optional PC heroes in several cases, with artwork, plus most of them include maps.
DH also has seven Star Hero adventures, three for Fantasy, and a couple for other genres.
DH Adventures .doc
