And if they don't abide by the contract then they get the belt taken off them. But whoever wins will just vacate the belt anyway and go back to 154.

Didn't the WBC pull this exact stroke a few years ago to convince some other high risk low reward guy that he was guaranteed a massive payday, only for the two potential paydays to head off in other directions after they fought?

I forget who it was exactly but this same thing happened a few years ago.