[The key to this would be profit....]
That's actually the key to why it'll never be allowed to happen. The current system already includes GUARANTEED profits - which DOT euphemistically calls "management fees" - for all seven carriers, as well as coverage of ALL expenses, including (but not limited to) executive salaries, wages, campaign contributions, liability settlements, and "penalties" for lousy service. With such a deal, the carriers and their City Council lackeys will maintain the status quo at all costs.