Since I am interested in hardware monitoring and single-stepping through bus cycles, 6809/6309, 8051 and many others (not capable of stopping in the middle of bus cycle) are somehow out of my scope. We have MC68008 variant already and I think of MC68000/010 and Intel 8080 - schematics are ready, working on the PCBs.
The MC68000 board, incorporating the STM32L496 MCU, will have the size of DIL64 socket, so if I succeed, this will be the smallest DIP64 MC68k computer in the world.
I believe that USB power and interface is the way to go for modern retro computers.
No more power supplies and RS232 consoles...
Thanks for interesting links.