It used to be that it was possible to recruit him again, if you knew how to find/scout him, but I think maybe they changed that when folks complained about it.
I understand your position and don’t agree or disagree really with the stance. It is what it is, IMO. Best practice for a coach in your position, if the guy is important to keep, more important than winning games this year, keep him in the starting lineup. Don’t adjust the depth chart at all. If he’s too injured to play, he just doesn’t play; when he’s ready to be back in, he’ll expect to be back in, and if you never take him off the depth chart, he just jumps back in. Then you don’t have to worry about knowing exactly when he crosses that line (since the system doesn’t tell you, which is the one uncontroversially stupid part of this process which absolutely should be fixed) into “healthy enough to play.” There is really no risk of re-injury. Even if it does exist (I’m not convinced it does) injuries are so rare in the first place, it’s not enough to worry about. Certainly doesn’t compare to the risk of losing the player to transfer.