This was just a random thought that popped into my mind.

What would be stopping me from purchasing a camera/ gimble combo from the Mavic Air2S and replacing the one on my Mavic 2 air with it? It seems that it would be a simple swap on the hardware side given both are on the same platform. The only concern is on the software side. I know the pricing of a new camera and gimble for the Air 2S make this seem like an illogical upgrade, however I would be interested to know if anyone has thoughts on whether this is feasible.

Theres no way to upgrade the firmware on the drone to that of a different model.

You're right as it is an illogical upgrade.  However, the showstopper will be not being able to update the firmware on the Air 2 to Air 2S firmware.