The idea just, well, hit me.
A "magical girl" MMORPG.
Stick with me a moment here, lemme walk you through it...
You have a nice fictional Tokyo, with all sorts of neat sights and created maps, where our players hunt monsters and have occasional Fight Club PVP battles. They're all hunting down monsters and critters and creatures and all the naughty things that go bump in the day (and the night). Girls-and boys-of all sorts are on the battlefield, trying to make Tokyo a safer (and PG-13) place...
I can even see the character archtypes-
Cosplayers-They can change their powers by their costumes. Higher levels mean more interesting costumes...
Meganeko-Gadgeteers and Weird Stuff creators. Occasionally blows up property in the area.
Miko-They cast buff spells and healing spells. Oh, and can banish some kind of spirit critters.
Joshikousei(and whatever the male version is)-Major sailor suit action, with all the fun and excitement that brings. Divided into the ones that actually use weapons and the ones that are spell casters.
Tsundere-Years of harem abuse means that these are the game's "brick" characters.
There's probably a "gun otaku" character type a'la Sosuke Sagara, with options of "real world" or "sci-fi" guns. Add a Martial Arts template, too.
So, our (of legal age-18 and over) characters go out and make the world a better place-hopefully without doing too much property damage. The various districts of Tokyo serve as a way to control character levels (and it all converges on the center of Tokyo...). Map-accurate, too...tho not probably "ground-level" accurate.
Probably can pull this off with most current MMORPG engines, but I would definitely want the whole "high anime" aspect to the graphics. Lots of explosions...and havoc and chaos and panty shots. Real-world clock as well, where players are on Tokyo time. And, some monsters are out during the day, some are out during the night...
I'm almost tempted to add a connection so that you can play iTunes native to the game.
So, anybody want to start throwing more ideas up against the wall, to see what sticks?