Monster of the Day Community Reroll
Implement an NPC right next to the Monster of the Day showcase, its function would be to reroll the Monster of the Day once the community fee has been reached.
I think a good fee would be something like 5.000.000 total for a reroll. However, to prevent trolling, a second option would need to be enabled, once a reroll objective has been reached, it would give players a 10~30 minutes warning before the reroll takes place; during this time, players would need to pay 1.000.000 to prevent the reroll.
Sometimes, Monster of the Day rolls some really crappy monsters, and sometimes it goes on for days or even weeks. It is also a small zeny sink.