In my opinion, it's not about what we "gain". It's about protecting the integrity of the league's by-laws.
The question is pretty simple: Can institutions sign/agree to a legal contract, then turn around and do whatever the heck they want to do?
Would you want a situation like this to happen to the Sun Belt? If Ga State, App and Coastal were invited to another conference, wouldn't you expect them to follow the by-laws of the SBC?
I'd hope you would.