There's one thing you guys are missing out on, and it's the one the FAA can and will get a PIC on every time. I don't have my regs in front of me, but part 91 says the aircraft must be operated safely and prohibits "wre3ckless operation". That is entirely subjective, and for the investigators to determine, and there's not really any way to argue it.
As a part 121 crew, there are certain things that we just cannot do, although it is not specifially prohibited by FARs, this would be an example of one.
Another example: we cannot just do a low approach/fly by at an airshow with a load of revenue passengers.
Also, I don't recall the exact wording, but formation flight with any revenue passengers is also prohibited, other than some exceptions (which I guess is what was being discussed above?)
If SWA were just a standard part 91 repo flight, then this would be a completely different scenario. A part 121 flight is held to a much higher standard than a part 91 flight.