I would train such a person the same as anyone else, that is, try to teach good form and use as a primary training weight the most weight he could so with consistently good form.
Ive actually coached a LOT of guys like this, most came from PL, very strong and had done some powercleans and such with horrendous form in high school or whatever. The first ever national junior squad member and one of my first national champions was such a guy, Justin Schlager. Good kid, came to me with a 400lb bench, 600lb Pl squat and deadlift. He was doing 130kg snatch and 160kg clean and jerk in less than a year. Good kid.
Since HS powerlifting is a varsity sport down here in Texas, i have gotten a lot of these kids right out of high school, strong from powerlifting and have done their particular football coaches version of powercleans and maybe powersnatches, but WILD technique. Most of them have done well in OL within a year or two.