I think a fine tooth benchtop bandsaw would give you better control. If it was me I would probably try to find a speed and feed that worked on the little CNC router and cut them out in batches with tabs holding them in the sheet until I am ready to break them out and finish off the tabs on the sander.
I think it was Vodkaman who came up with the idea of using an inverted sabre saw in a table to get a bandsaw like experience without going the expense of an actual bandsaw.
A rotary tool with a slitting saw blade might work ok, but I am not sure I would want to cut any kind of resin material like circuit boards with either a particle of fiber cut off wheel. I keep a rotary flex shaft hanging on the pegboard all the time, tooled up with a fiber cut off wheel, but I only use it for cutting metal. Even aluminum gums it up faster than it can cut. Brass and steel cut nicely with it though.