I think enforcing by legislative means the profit-sharing system traditional players have with the airports is completely unreasonable. They go out as far as to call it a safety issue.

Yes, the playing field is not level, but that's what competition means: the sharing companies have found a way to go around the onerous taxes imposed by airports and there is almost nothing the airport can do to stop a private individual drop a car in it's short term parking lot for another individual. There's no safety or congestion issue, it's the entire point of the short time parking spaces.