He already has ways, AFO has his face fucked up, he is no match for post operation AM, even if he transfers his quirk to shigaraki without the quirk control experience AFO developped over years of living, Shigaraki wont be big deal, yes he will be able to easily destroy other quirk users on a daily basis, but due to lack of quirk experience, he would be a easy prey to more experienced quirk users like Todoroki, Mirio, etc... provided he doesnt go close quarters on them, then it´s a guaranteed win for shigaraki. The only problem I will have with the series is if, the hyper regen quirk comes back into the plot, as a power-up, tor the AFO user, that would be extremely haxed, especially taking into account the speech the doctor gave, on that quirk, it´s really broken hax to hear that AFO could´ve come out of his fight against AM with pratically no serious injuries, just because of that one quirk alone, it ruins the tension of any fight between a AFO user and whoever, he/she´s against, if the viewer knows that quirk will come into play.
About Deku he wont have time to master OFA in the amount of chaps this series is supposed to last, we already talked about this before but he aint getting 100% mastered without a really big time, skip happening, way bigger than a 2-3 year one anyways, if he ever reaches around 20-25% mastery by the time the series is over, it´s already gonna be pretty good and consideering the injuries he took to his arms for overusing OFA beforehand he wont be anywhere near prime AM level, the series really tries hard to showcase that none of the heroes at Yuhei really are prime AM level material, especially in the determination department, on a general basis they (new hero generation) will surpass all other older gen. pros and set a new record for the Top heroes, both powerwise and ideal wise (to overcome the issues that created the stain mentality) yes, but there aint gonna be a 2nd AM, it´s also not healthy for there to be one because it has the risk of creating Endeavour cases.