I can't think of a reason a group of modern-day friends (in a fantasy world) would go through the sewers; since that's the only dungeon I can think of making them go to; it's a dungeon crawler type game. XD
I've been working on plugins to make it easier to incorporate Persona 3's Once More batsys into MV games. One makes it so you can have states automatically applied to the target and/or user when their hit crits or targets a weakness... I could use testers for it, though. Maybe I'll make a thread in the JS Plugins In Development board about it?