i agree that it will probably be a kinko's business model. as the price goes down and other materials become available, it will still be too expensive to operate any of the printers that can put out functional items.
knicknacks and other arts and crafts can be done in plastic or any of the bonded powders, but anything function will require a homogeneous composition(injection, die, metal infusion, or sintering).
the printed AR receiver and mags that that guy tried to print failed after 2 or 3 shots. mainly because all printing processes are layer depositions which builds in thousands of stress failure points. the compression strength of most printed items is ok, but the sheer and torsional strength isnt anything you would want to put any real weight or force on(at least not the plastic extrusion type printers, and probably not even the laser cured resin types).
metal printers just bind steel powder into a temporary structure that has to be infused with a molten metal to become functional. that kind of brass or bronze smelting isnt for the home brewer. even the resin impregnating of the starch powder types isnt that fun a process.
a franchise 3d print shop would probably be a combo of 3d printing, rtv rubber and plastic mold casting, laser cutting/etching, metal sintering and cad cam milling with something between consumer and truly professional equipment. you would bring in your project shape and engineering criteria and the staff would help you figure out if you should print it, print a mold so you can cast it, or mill it from metal/wood.