Just a couple of points Al
Your Roto-Zip runs at between 18,000 and 25,000 rpm. And if you could mount it rigidly enough would probably do light milling great. Building the mount would be prohibitive though.
But in the same vein as attacking it from a different direction.
I make no claims to being an accomplished machinist or tool maker, but....
Have you thought about using a slot cutter? Like cutting a Woodruff Key. And mounting the trigger guard 90° from the spindle? If you are relieving for trigger travel on the inside of the guard, the cutter radius might actually be beneficial. Not to mention it being possible to be closer to the spindle and stiffer.
