Of course, the first thing that comes to mind is the LOGO limited release for the Vectrex which seemingly does this. (Or LOGO Lite from Madtronix). Check those out. Maybe a bit hard to obtain now, but sounds like exactly what you are looking for. It would be nice to do something similar via Vectrex32, but it sounds like it would have to be designed from the ground up - and still would not be able to save to memory.