Check anything with R-18, and you have your shmup H-games
Try jerking off while the bullets are coming at you. That is, the H is not something that occurs when you win or lose; instead, it occurs as you play, so the longer you play (eg: survive) the more you see.
I think that would be fairly popular amongst hardcore shmups fans
Sounds like a great idea maybe I will grab the shmups engine and see how to customize it as such.