Graynomad:
6809 was the best 8-bit microprocessor ever made, I ordered a couple while they are still available.
I used to program on a 6809 as well. How about we make a retro dual processor (09/Z80) board
compatible SRAM and some program storage memory that is relatively easy to program as I have no idea where my EPROM programmer has gotten off to. Any recommendations welcome.
There's plenty of SRAM around these days that will work. As for the EPROM, maybe use flash or just battery-back the SRAM. You could build in a modern micro to act as a programmer.
Another idea is to have an modern micro actually serve the EPROM data.
Rob
I would certainly be willing to work on the 6809 half. 
I had a Z80 CP/M machine (Big Board) but didn't do much hardware development on the Z80. As I recall though, it was very Motorola like at the bus level so it would be a good match.
I have already started thinking about the memory. Battery backed ram might be the way to go. On the other hand I was thinking about building a programmer for EEPROM that ran off my Raspberry Pi. I have already compiled and tested a cross assembler that runs nicely on the Pi and I thought since the hex files would already be on it it would make sense to use it for the programmer.
How would you propose serving the EPROM data via micro?