That's already what FlightCar is doing: their facilities are all off-airport, in another city 5 minutes away.
The valet drop-off/pick-up service (and air-travel-related marketing) is what SFO thinks entitles them to the rental agency fees... even though the drop-off/pick-up is indistingushable, in terms of impact, from having a friend drive you.
The valet drop-off/pick-up service (and air-travel-related marketing) is what SFO thinks entitles them to the rental agency fees... even though the drop-off/pick-up is indistingushable, in terms of impact, from having a friend drive you.