I'm pondering a metroidvania MOBA based on 8-bit Bruce Lee. The grunts are ninjas, and "pixel rivers" replace towers. Grabbing all nearby lamps flips flow.
Powerups are new moves, such as the ability to jump diagonally, slide attack under obstacles, and move left/right while falling, as well as speedups, jump height.
When hit, you lose powerups in reverse order. You recover all powerups when respawning.
So, you usually want to slow down enemies rather than kill them...