Just spit balling here, but how about a zone that celebrates the game by using NPCs from the earlier story arcs, radio/paper missions, mayhem/safeguard missions and morality missions as contacts for new mission arcs and task/strike forces of different level ranges. Fusionette is already a trainer in this zone, so this kind of expands on that.
For example, let's have the Frostfire strike force, where the former villain brings you in to help fight a mystical threat created when some Hellions fooled around with some very dangerous artifacts. (Yes, I know some players may have killed him in some vigilante tip mission, but hey, he reformed in the mission I ran 🙂 ).