If the token shoefoot may offer another perspective...The more it's an issue the more stubborn the hairier sex gets. So, yeah, just drop it for a while. That said...Is it the Adams that he has from Altra (yes I am too lazy to re-read the OP)? I'm running in the Instinct 1.5 and the Lone Peak currently. He may bite on either of those, and here's why: 1. They look closer to what he's used to in a shoe. 2.They do have some stack between his foot and the ground (but are f-l-a-t). 3.If he is worried about his PF/heel issue, he can fit an orthotic in there to start out if needed. I have a flexible over the counter footbed that I have to use from time to time with my ball of foot issues and it will fit in mine (Sole Thinsport, just as FYI) without lifting my heel completely out of the shoe. 4. (arguable point alert) you get a lot of the benefit of barefoot (i.e. toe splay, neutral posture, urge to mid/forefoot strike) without the full on flying of the freak flag.
My $.02 (and it's worth about that much)
My $.02 (and it's worth about that much)