Baylor has zero incentive to agree not to sue the SEC or A&M. They will lose so much money if the Big 12 collapses since they know they will not get into a "superconference". They only got into the Big 12 because the governor was an alumna.
Baylor may not be a great football program (which is where the money is), but overall, they are definitely one of the most competitive athletic programs in the Big 12. The money they bring in for Football is what allows them to be so successful in all the other sports.
It could also be that Texas is behind Baylor not agreeing to not sue. Texas does not want to go independent in their olympic sports, and they know they will have to restructure (read: lose money) their TV deal if they enter the Pac-12/16.
The SEC will have to drop their requirement that a team be free from potential lawsuits if this deal is going to go through. Baylor knows they that would be committing suicide by agreeing not to sue A&M. They are not going to do that.