The semi "kits" for the 1919 are expensive--a bit TOO expensive actually. go to www.1919A4.com and you can find links to other build sites such as "shot in the dark" where you will find diagrams of the SA trigger modification. There is some variation in dimensions and details between different "designers" though all follow the same basic planform. The companies that market the SA kits aren't interested in revealing a lot of specs, because then every intrepid machinist would do their own.
On virtually all sites concerning the 1919 you can find the legal aspects of how one must be assembled to make it legal--notably, a right side plate that starts out .250" thick, then milled along the inside to create a ledge, with corresponding milling of the bolt, barrel extension and lock frame--this prevents installation of FA parts once the gun is assembled. The RSP must be deep-welded to the barrel trunnion, and bottom plate so that it becomes an integral, non-removable part. The SA trigger parts aren't really that complicated once you see how the gun works. A new sear release must be machined, along with enlarging the mating slots in the bolt. The trigger is modified to a "two-piece" with the forward section becoming self-disconnecting as the bolt opens. If you can do the mill work to complete an AR15 lower, then milling the SA parts for a 1919 would be a piece of cake.
As for the Mini-mill...I've used mine to mill numerous 1911 frames, Sig frames (both steel and aluminum), revolver parts, rifle receivers, etc and have never found it lacking. As with any piece of machinery, much of the "output" is determined by operator skill, knowledge, and set-up. I milled Sig frames clamped upright to a heavy, 6" L-bracket sitting on top of a 6" rotary table, and still had clearance to raise the head and clear the bit...as for "power"...believe me, you're more likely to shatter a mill bit using too heavy feed than to "bog" the motor.