I will be following this thread to see how you go, looks like you are off to a good start.
Have you thought of using a permanent marker instead of a cutter ? I did a board today as a matter of fact, and as I had a little unused room around the board so I drew a happy face with a permanent marker to test as I had heard it works as a resist, and the result was pretty impressive, the edge definition is perfect.
You can get drafting pens down to 0.2mm (0.0079in)that you can fill with whatever ink you want to, easily small enough to do even most of the surface mount stuff. It is something I want to try eventually, as you said with a dedicated machine.
A second hand plotter would probably save a little time as well.
I took a pic so you can see what I mean.