Heck, it is yours so do what you want to do to it. I find some of the questions about "collector value" funny really. When I asked about sanding my Tarwar's finger grooves down my concern wasn't so much about what it was going to do to the value or it so much as whether or not I was going to be honoring Bura's wishes by doing so. I think in the end the consensus was that these folks make them to be used and if it is something that makes you use them more then do it.
As for the whole handle ring dilemma in general, I find that if you are holding the khukuri properly, they don't hurt you or make a blister but rather enhance your grip and make it a lot easier and more comfortable to retain control over the blade. Of course this assumes one has man sized hands. If one is not as well endowed as most, then I suppose said ring might become a more of burden than a blessing.