Aha! You know, the Fine Feed on most mini-mills IS a worm gear and knob setup. So perhaps the rotary broach WOULD work on a mini-mill, if advanced using the Fine Feed. I may yet give this a try. Especially since most of my projects are other than ferrous materials.
One thing I've learned in 15 years of working on mini-machines is that they have capabilities reaching far beyond what most people expect of them. It just takes determination, belief in the machine's potential, sometimes a few upgrade mods, and sometimes tossing the "books" and experimenting to find out how YOUR machine works, compared to how the old-timers tell you how it's done on professional machines.