What if, and hear me out, it was a roleplay based on a blank, white space. And you got to put anything in it? And the end project would be our supposed characters living in this world that they've created. Whether it be a fantasy world, starting off with someone creating some sort of mythical creature or being. Or maybe a casual house where our characters live out their day-to-day lives, starting off with something as simple as a couch.
And the best part is, we never know what they're gonna do. Maybe someone will create a humanity-destroying being and everyone else will have to fight it off! 
So how 'bout it? I hope this still qualifies as a roleplay- I'm honestly scared it won't.