I think the long term answer is to copy the rules for aviation, where a Private Pilot Licence is different from a Commercial Pilot Licence, and the rules about what the holders can do are clear and widely publicised. "Uber for planes" would be highly illegal, and everyone involved would get arrested.

Even without regulation, there must be a huge legal risk that Uber's lack of a serious fatigue management system will be found to be negligent. The ways this goes wrong in the trucking industry are very well known.