This is a serious question, and I desperately need your advice. Power sanding a tattoo off?

Serious answer. Absolutely not! tattoos are never removed this way. If you wish to have the tattoo removed safely see a board certified dermatologist who performs laser tattoo removal (with a q-switched laser).
Absolutely DO NOT! First i would hope your would have thought about this prior to getting the tattoo but now that the damage is done, it may be possible for you to have some laser treatment by a certified and qualified dermatologist to remove the tattoo. If it is a colored tattoo, you may have more difficulty removing it. You, yourself, should in no way, use a power tool to remove the tattoo. Don't do it!
You will be sorry. I had a patient do just that and it was a horrible outcome. What would have been a simple tattoo became a painful infected arm with secondary scaring and disfigurement. I assume you are doing this for speed and cost savings. The pan and secondary consequences are enormous. If you cant have it lasered then keep it.