I guess it really depends on how many students you are going to loose to something as trivial as bowing. If it is so much so that you will be worried about keeping the lights on, then I would say simply come up with something for your school as a replacement. If it is just one or two, then tell them that respect is a huge part of martial arts. If the DMV won't give a blind person a driver's license because he physically cannot see, they why give a black belt to someone who mentally cannot (or down-right refuses to) perform a certain part of your art?
This may seem harsh, but then again, they are damning me to an eternity of torment... so I guess we are even.
