Like the linked post, I think that the only way for P12 to get OU and UW to sign something is to create an acceptable "out" if they are invited to a better conference.
If we are being strict about terms, though, a 'Grant of Rights' doesn't really do that. It is an assignment of your media rights to the conference. Can you include provisions saying, in essence "unless we pay you enough money, then the rights are transferred back to the school". Sure, I suppose you can. But that is something very different from the 'Grant of Rights' that we began discussing a decade+ ago, which was meant to provide conferences and TV partners with clarity about what content they secure as part of a media deal.
In short . . . P12 must look very, very weak to TV partners in negotiations if they can't deliver a "true" GOR with all members. Tough position to negotiate from for the conference.