Yes I have contacted him a few years ago and he said he would let me know when he would build them again.
Your idea with the serial connection sounds good too. It's like Rene's C7050.
Yes I think it is doable, only difference is that the serial port would not be connected to the cartridge but to the vectrex' controller port 2. I am not sure what baudrates are possible as every bit should be timed in software. My knowledge of interrupts and such of the vectrex are still limited. I do know the VIA 6522 a bit, I also know it has a hardware serial shift register but it also has a nasty bug and the serial in/out is not connected to the controller port(s) but to the vector hardware anyway.
Without screen generation the 6809 should be capable of steady baudrates without problems. A converter cable from the controller port to RS232 should be no more than a MAX232 and some small caps. A standard D9 connector has to be modified a bit to fit but maybe I can get some joystick extension cables to cut up.
