If you want to have a look at luaprinter, I have a branch at:https://github.com/goldnchild/mame/tree/luaprinter
I need to clean it up and figure out the proper way of doing things using the device_interface mix-in.
One weird thing that the ap2000 is doing is that it's missing descenders when it prints in the Roman font. I thought initially that it wasn't getting the full 9 bits of the printhead, but it prints draft just fine as well as the Sans Serif.
Ramiro Polla (the uber-hacker behind the ap2000 driver) was cool enough to send me his ap2000 disassembly so maybe I can figure out why.