Thinking about it a little more, Dremel does have a locking depth stop, but you'd still need a way of patterning/transferring the shape of the t-nut... in woodworking, this would be done with a template being traced either by bearings mounted on the cutter shaft or with a concentric bushing... This might be a bit much to ask when working within the confines of a shoe.

I do wonder if you actually need that precise countersunk shape, though. Let's just say that you made a round countersink that would allow the t-nut to spin... you could use adhesives but it might even be fine without, you just need a finger on the t-nut to keep it from spinning until it's tight enough for friction to keep it in place. Hell, a bit of Gorilla/duct tape over the top of the nuts might be enough to keep them from spinning until they're tight enough...