The killer feature for Uber/Lyft is being able to get a ride at any time on demand in a matter of minutes. It doesn't seem like this will be able to get there.
I have wondered if a pure market making app would work... let drivers and riders place bids... a driver can lower their bid to get hired faster and a rider can increase their bid to get picked up faster. The app would just take a fixed cut.
Someone who doesn't mind waiting at a friends house for a while longer could pay less, but the person in a rush could get a ride fast for a bit more. Similarly, some drivers might be ok only doing a few expensive rides.
I know Uber does something like this with surge pricing, but it is not transparent at all, and you can't change your bid.