Bare with me, and I think the most important thing would be an appropriate RP angle (I interpret that as being the biggest risk factor).

What if once a month, for a 72 hour period, the mud turned into a "version of the future" (my only attempt at an RP angle so far) where it's a clean slate CF, all gear reset to mobs, and all the pfiles are hero leveled (or appropriately set for goblins, orcs, necromancers(?)) and any newly created player would be set to hero (this would most likely need to restrict characters created from a single IP, be it 10 minutes or something more significant).

After the 72 hour period, the pfiles and everything would be restored to the moment before "the vision" began. Ideally, RP would stay intact, but could possibly appeal to many players? Otherwise, it could be just that I'm sleep deprived.