The NCAA shouldn't buy the players insurance, the players should buy it themselves.
If the players don't have cash for a policy, they agree to give up a % of their salary should they be drafted.
It isn't that complicated, but I'm sure someone will try to over-complicate the issue with nonsense regulations.
You can't pledge future wages as security for a financial obligation.
A work-around I toyed with once (in the theoretical sense...not that I had the ability or desire to pursue it...) was a specialty lending/finance company providing loans to likely soon-to-be professional athletes. The inspiration for the idea was the osu memorabilia sales thing. What if instead of selling those items, the players pledged those assets as collateral for a loan?
With the insurance situation, what I think you could do is borrow the money to pay for the policy, but then pledge the policy itself as collateral for the loan. There shouldn't be anything controversial about that from a legal perspective since insurance policies are provided as collateral all the time.
What I never sat down to figure out was how NCAA compliance would look at those things. My guess is they'd be OK with insurance but not the memorabilia.