It always pains me when someone or some institution doesn't want to do A Good Thing because "it might create a precedent". I like the concept of the "declared non-precedent". The application for this is when you are going out on a limb to try something, but if it doesn't work, or causes an unsustainable rush of "me too" requests, you reserve the right to disclaim any precedent.
I've tried this at work a couple of times, it has worked okay. In those cases, I have been in the position of supplicant--not decider--and have assured the powers-that-be that in no way would my request be construed as precedent.