I would think you would have a hard time, legally, requiring anyone to pay the deductible portion of your insurance. After all, it's your insurance, you took out the insurance and decided on the deductible. How about a system of fines, instead or firing him for not following the rules? How are you going to collect? Just withhold his paycheck? Then he'd just quit and you still don't collect. Interesting situation.
if it ain't broke, don't fix it