I don't believe that the suspension was the only issue with Grier. Look at the father, look at the family. It's a me first attitude and a look at me environment. We all know the rumors about the partying and issues there. I think Treon starting was some passive aggressive mind games with Mac. I also think the suspension was beyond the last draw. We certainly don't know what all happened, but my thoughts are that the kid was a cancer on the team and Mac had an opportunity to jettison him before it affected the locker room. I hate that he had to leave, but I really don't think it was just over the suspension. I think there was much more to it.
We certainly don't know, but we're all allowed to speculate, and your "thesis" sets the groundwork for what may have happened. This was Muschamp's broken team he inherited and from the earliest acts, which included the over-the-top sideline rant at Taylor, Mac was the new dog marking his territory.
We all shook our head over him having Grier and Harris even when it was so obvious who was the better quarterback. Mac felt he had to test Grier before he was willing to give ground. When Grier got suspended, there was yet another test, this time sterner. I'm personally convinced what happened in the decisive meeting didn't amount so much to a demand for the starting time, maybe not even so much a demand for time, but more a kid looking for acceptance.
He knew he was better than anyone else on the roster. Why would he have been paranoid about not winning the job back on the field? Because Mac was back to marking territory, only this time worse, much worse. He didn't like the kid's cocky arrogance and he had even less stomach for the father.
Yes, it was Grier who made the decision to transfer, but at that point the relationship was pretty much kaput. If the kid was willing to risk that much, it couldn't have been a good situation. No one flies off the handle that easily and risks their career, and I don't think Grier did either. He knew he had to go.