or they could treat them signing the letter of intent as a binding contract and have them written as such.
"you said you'd play for this team for 4 years. if we don't play you as a freshman, then you still have 4 years of eligibility (like being red-shirted). if you don't play as a freshman and then play 2 years with us, then decide to transfer, then you only have 1 year left of eligibility. but, because of that, you are eligible to play right away at another school.
basically like a red-shirt...except they burn one year if they transfer...but they are eligible right away at their new school.
regarding injuries:
if they're injured and are out for the season before the 5th game of the season (basically 1/3 of the season), then they can opt to count that as an injury/medical hardship (or whatever they call it); and they still have 1 more year of eligibility left. BUT...they only get 1. PERIOD...END OF STATEMENT....NO EXCEPTIONS! and make it to where it is NOT negotiable in any way, shape, or form. as in...they won't even HEAR a case like that if it's brought up. it is instantly denied. i'm really tired of seeing guys being allowed to play because they got injured 2 or 3 times and they're almost 25 years old playing college football after joining the team when they were 18. i mean shit...do you really wanna play college football that much? do you not have ANY aspirations of trying out for an nfl spot? i hope they got a degree in those 6-7 years they were in college. hell, they could get a masters in most subjects in less time. so they need to cut that off starting...oh...about 5 years ago.