The GOP can avoid Jeb being nominee if it is willing to forego the usual circular firing squads. Which means being willing to countenance the less-than-perfect which is still better than Jeb. Otherwise he will be the lurker to come out from behind the shadows after all the not-perfects have slain one another. He will have won that battle because he will have refrained from participating in it.
I think a good example of that is Perry in 2012. He supported letting illegal alien children get college financial aid in the first debate, and it seemed like that destroyed him in the eyes of conservatives. But he’s solidly conservative, as he has proven repeatedly.