I think people have successfully done much worse than this. I've heard of a trick where you use Air Canada *G status to get into a United club on a domestic itinerary, and then switch back to MP at the gate before the flight.

You could probably just leave out FF numbers on the itinerary and retroactively claim each segment with a different airline. But in that case you wouldn't get status benefits on the flights (assuming you have status).

Not only is it possible, but you can also do it without any GA interaction.

While you are waiting between flights, just log-in to .bomb and swap out your FF number in My Reservations. Then go reprint your BP or refresh the BP on your phone.

One thing I noticed is that it does not affect your position on upgrades. So if your CPU was requested using your UA number/status and you changed the FF number afterwards, you are still on the waitlist according to your UA status.

Of course, this only works if you have access to .bomb (and not the mobile app). Even if there isn't free WiFi at the airport, most paid airport WiFi areas allow you to access .bomb for free.

No guarantees here, but for some flight combinations the connecting flights do earn miles in MP even when, if booked separately, the flights would not be eligible to earn miles. There is no language on the Air Canada page about this exception, but I have benefited from it on LH and LX multiple times.