This market type would be a dead simple experimental playground: People can pay in mana (perhaps also other assets), the creator can pay out. It's a pretty transaction table.

The creator can use the market description to define how they'll act, letting them try out exotic market types like 

https://manifold.markets/tailcalled/will-manifold-markets-have-builtin

If creators keep using some rule, the devs might add support for it - for example, if creators keep saying "Users can name a price at which they'll sell their future payouts from this market.", the devs might add a "users get a button to name a price at which they'll sell their future payouts." toggle.

This is a logical extension of Manifold's core idea: Market resolution is an unsolved problem? Let humans do that part. Various arcane market types aren't implemented? Tear the market mechanisms down to sand, let humans hold it in whatever shape they'd like.