The proposed alliance is not out to harm the SEC but rather check it. The alliance would still want exposure in the Southeast. To create a league excluding the SEC would be a frivolous as the SEC going it alone, each side would alienate a significant market to their detriment.
The NFL works because the entire country is covered. What makes anyone think CFB would be different? CFB could be regionalized but that weakens everybody, possibly even the networks. I remember my years in CO, LA, and AZ, while a die hard Orangemen fan (as we all were back then), I would watch what games against could and catch a local game but I had no interest in most of the other nearby (relative term) teams. Having friends, families, and lives, most of us cannot watch CFB all weekend so we watch what we want and work around our preferred games. While I enjoy LSU, AZ State, and TAMU, I don't often make time to watch them as I will watch SU and then watch other games as time permits.
The alliance is more about keeping the SEC in check and maintaining relative balance among the P5(4). Eventually, the schools and conferences will realize their tru bargaining power is as one unit, like the pros. Until the, the networks, especially ESPN, will have the upper hand in controlling payouts and keeping some teams up and other teams down.
Just my take.