Me thinks that the Insurance Companies might have the final say......
Somewhere in the insurance policy will be something along the lines of "...aircraft to be operated in accordance with the approved flight manual ....."
Also, the TCDS A16WE which covers all the B737 series it has the following included for all series "Airplane operation must be in accordance with the FAA Approved AFM".
Somewhere in the AFM (don't have one to hand at the moment) it will state the normal operating crew compliment....shoud be 2.
Therefore, for Mr O'Leary to operate with one crew, he will be operating not in accordance with the AFM, and not in accordance with the TCDS, and therefore invalidating all his insurance policies......not a very wise business decision.......if he wants to do it he has to change the FAA's mind.....not an easy thing to do.
But don't let that get in the way of his plans...........