I think this is actually common now. I'm often asked to make a deposit on a reservation when using Resy.

I'm not aware that there is variable or dynamic pricing component to it, however. That's a great idea and something I bet they are considering.

In practice, dynamic pricing it is not a panacea. You still need to beat the arbitrage market. Charge too much: customers don't reserve. Charge too little: brokers snap it up.