Simply put, a server where admins could plan events, prepare, build, all without worrying about space, players, performance, dropped loot, etc. This would open the entire map for admins, and conjure up new ideas that basically weren't possible before. Custom maps could even be used, like on Elysium, so that specific events could take place (road that allows for a race around the map, huge mountain like last wipe, etc.).
And with no pesky active players to worry about, changes could be made on the fly for the event (change day/night, call in 40 Karens, etc.).
Ideas off the top of my head :
Car race around the map
The Karens are coming! (mountain top base, defend it at all cost against wave after wave of Karens)
Horse racing track (all thoroughbreds obviously)
Boat rally
Snow mobile race
Treasure hunt in scrappies (pilots register beforehand, each assigned to a team)
Or simply team treasure hunt on horses
Car jumping (huge ramp, sedans, 3 tries each, longest jump wins)
Harbour Takeover (TONS of though NPCs, 10 mins to take em all out and takeover Harbour)
Drag racing course
Team raids (30mins to build, PvP turned on, last base still with TC wins)
Rock climbing (first to reach top of a huge mountain wins)
Medieval battlefield (choose archer or knight? Two clans meet on an open field, war!)
I could go on ...