Seems if he's going to be ready by the start of summer camp, it's fine. He knows the offense, obviously. This will give the new guy plenty of work to get up to speed. Odds are he'll be called on at some point next season.
There are a number of guys out there, though, who have great metrics and have thrived against lesser competition at the high school level. The step up to P5 ball is big for a lot of them, and if you can't block or tackle or run routes or cover guys who do it at a high level, too, you're going to...
I'm concerned about the guys here. How invested are they based on the way they're playing, their intensity, etc.? Once upheaval starts, it doesn't just stop.