Well a friend of mine, Luis Antoniosi has designed an 80 column video card for pre-Coco3 Color Computers that uses the Yamaha V9958 video display processor.
This also has sprite graphics, higher res modes, and a great range of colors than the original 6847 VDG was capable of.
He has working prototypes of it and we've just received the first circuit boards back from a Chinese production run.
He has OS-9 and BASIC drivers he's working on.
And we've talked about adding an OPN4 sound chip to a future board.
So 6809/6309 based hacking continues...