I'm kind of wondering what the definitions of a mini mill are on this board. I view mini mills as the small benchtop machines made for making model parts with a slide travel of less than 12". The one link I saw for a Grizzley machine is a knee mill and certainly not what I would place in this category.
As far as the inletting goes I don't mind using one of these machines to inlet a straight octagon barrel, though that is about the limit of what I would consider it good for, other than perhaps drilling holes and cutting a rough mortise for the barrel tang and triggers. Fine inletting is still best done by hand, though I will admit using the dremel tool in a router attachment for some aspects of lock inletting, though again for the plate I would never inlet that with a machine such as this. A stock duplicator is another matter entirely, though I doubt I'll ever have the cash to buy one good enough to trust to work of that nature.
One thought that is often mentioned concerning power tools is the realty that most early smiths had apprentices that they used for some of the more tedious tasks of the project, I tend to think of the power tools available today as a suitable replacement for the apprentice. Plus, I bet if some of these tools had been available to the same early smiths they would not only have used them, but they would have liked them.