All that said, the company that outsources (and that's really what you're proposing) such a core component of their business is probably taking on way too much risk.
One thing I thought, it would be really convinient if Uber could amortize their surge pricing over the month/year. In order not to hit customers with unexpected rates and essentially offer a flat predictable fee over the whole period. Problem with that is you can't really plan the future demand to calculate how much you need to save/dip. Could an auction house help to hedge the bets?
Surge is only really solved once autonomous vehicles can be preemptively positioned near demand.