That's probably possible, but you may have better luck on non-trivial circuits using the plotter with a knife blade to cut or a pen to draw masks, and then do p

That's probably possible, but you may have better luck on non-trivial circuits using the plotter with a knife blade to cut or a pen to draw masks, and then do photoresist etching. Or maybe you could draw with a Sharpie directly on the photoresist paint and then expose it, without masking material. It's worth a shot anyway. Plotter-printed photoresist masks were actually a fairly common way of doing PCBs in lab settings, back in the 80s and early 90s. Later, it became easier just to run acetate sheets through laser printers, but for a while a Rapidograph filled with India ink was the cleanest, darkest line you could get. Perhaps more usefully today, quite a lot of people use vinyl cutters to cut thin plastic (mylar usually) to make solder masks. Even the cheaper cutters can do a surprisingly good job of this, enough to make solder masks for many SMCs.