Far more complicated than the plan I had, but it does provide a usable (inrunner) style of motor.
My plan was simply to machine a mount, bolt it to the table,
ditch the endcap, brushes, etc off the brushed motor,
slip the comm end of the armature in the mount on the table and crank 'er down tight,
connect the three wires from the brushless ESC to the three segments on the comm. (pretty much requires you to use a 3 pole brushed motor, the most popular in use at this time),
the can just sits in it's normal place.
Sounds to me like a brushed motor just got converted to a brushless outrunner.
I don't have enough education or experience to know if it's just that easy, but if it works, proof of concept is done.
To make it at all usable one could machine an adapter that bolts to the PTO end of the can, and put some holes in it for mounting a prop or pulley.
If the original intent was to make an inrunner that could be bolted back into where the brushed motor came out of,
instead of bolting the mount to the table, bolt it to a square plate (or make the mount itself square),
make a similar square plate for the PTO end,
4 rods will connect the two,
the PTO end adapter previously mentioned can then get a small length of 1/8th" or 5mm shaft (instead of bolting on a prop),
the square plate on the PTO end will have a hole in the middle for the output shaft to come through, and two more roughly 25mm apart which is where you'd bolt it to your stock motor plate.
I think before I went this route, even a notorious skin-flint like me would just cut loose with a handful of 20's and buy something that actually stood a chance of working.