This ties in nicely with a conversation John and I had last night. Role-playing games tend to have certain conventions that may seem strange and arbitrary to outsiders, for example the arbitrary and dubious morality of killing monsters and stealing their treasure, and how that clashes with attempts to make games "more developed" by giving said monsters families and cultures and societies. In some ways it makes more sense to keep the monsters mindlessly, culture-less-ly evil: they're just swarms of goblins, they have no homes or families.
Well, there's another type of game that has similar bizarre and arbitrary conventions for the "worlds" where it takes place: the video game. I'm thinking specifically of the Super Mario Brothers and Sonic the Hedgehog type games. Players make up whimsical, cartoonish heroes, with a very simple and specific quest: rescue the princess and defeat the Big Boss. Opponents of course are somewhat mindless, endlessly spawned minions with no families for you to worry about -- kill at will. They don't really "die" in the messy blood-and-guts manner, anyhow, they just make a cartoonish grimace and drop off the playing field. Meanwhile, your hero is busy finding and collecting magic rings/tokens/coins and power-ups so they'll be strong enough to defeat the Level Boss and ultimately the Big Boss.
This would probably work well with the BESM rules. You could play in classic two-dimensional side-scrolling mode, which would offer interesting situations (and some cool feats, to use a d20 term even though I suggested BESM) to deal with, or go for the state-of-the-art three-dimensions. Heck, I just may run this myself as part of our campaign season break.