The problem is that you still need sophisticated tooling to get the barrel plate from what I heard.
However, doing a custom BS board would be cool.
Now that you mention it, there's no need to cnc milled metallic extrusion molds+ 50k equipment.
There are low technologic approaches to prototyping if you got a donor keyboard. To make a custom barrel plate you'd take appart single key sections cuts, order them like legos (copy, paste) according to the config of the final kbd, in respect of size, and angulation, patch the spaces between them and adapt the connection to the frame, or metallic plate of destiny with clay.
With the master prototype, a master mold could be made and then casted in plastic.
I don't know how to adapt the electronics of the switches to be able to register the key presses. A custom matrix and the soarer adapter could do.
I'm no legal expert, but as of now model M Patents are property of unicomp or IBM maybe, so if someone were to do this, it'd be for personal use only, at most.