If they could have scored LSU and Arkansas -- they might have been able to keep the others.
It might not have worked - but it would have been worth a try.
There's simply no way on earth that could have worked. As in literally no scenario imaginable in which that could or would have occurred. Let's forget about the sinking ship, let's pretend that part wasn't real. Let's just talk money.
Oklahoma and Texas want their money. They have been getting paid in the Big 12 (even if the others haven't) and part of their incentive to flirt with the Pac-12 is the promise of more money. Now, how on earth can those guys make what they make, and still cut in Arkansas and LSU to a sum so large that they'd leave the SEC? What do you have to do to the rest of the conference payouts to come up with 40+ million a year? You can't, that's the short answer. It's just not possible. This deal would have to be permanent to, right? They'd have to guarantee LSU and Arkansas
more money in perpetuity. Even if LSU and Arkansas would consider that, surely they'd know that would further destabilize the conference. The only way to make that work would be guaranteeing LSU, Arkansas, Texas, and Oklahoma the same gigantic sum of money. And disproportionate payments is one reason the Big 12 ended up falling apart in the first place. It just would not and could have have worked. Besides that, by the time A&M was ready to leave this was about getting away from Texas, not getting away from the Big 12. Texas and the LNH screwing them over was the last straw.
Now, having said that...
There was a point in time that Arkansas seemed to have some interest in the Big 12. This was well before things went south over there, and I suppose Arkansas wasn't happy with consistently falling behind Auburn/Alabama/LSU. I don't think anything ever went so far as serious discussions though, and I think the Big 12 seems very centered on Oklahoma and Texas, and what serves their interests and not so much in making it the best conference possible.
The one scenario though, the one that actually happened after A&M and Missouri was the possibility of Clemson and FSU. The ACC had just done a very basketball friendly deal and those two were not happy. I'm not sure how realistic that move was, how possible that could have been, but the only school the Big 12 actually seemed really big on adding was the long shot of Notre Dame. Ironically, even if just a partial member Notre Dame ends up in the ACC and FSU and Clemson stay put. Anyway, if the Big 12 didn't do everything in their power to add Clemson and FSU that was a big mistake. That's the one scenario in which they could have tried to compete with ACC money and do that they could to lure those two away. Then again, did Oklahoma and Texas want them around? Their interests as usual probably came ahead of the conference as a whole.