As you may already know, at the N8VEM project we are working on an S-100 VDP. This board has a V9939 video display processor and a AY-3-8910 sound generator which should allow us to have some MSX2 compatibility when combined with a backplane, S-100 Z80 CPU board, and a memory board.
There are more IO and memory features necessary for full MSX2 compatibility required though. I am considering a designing a board to provide the balance of MSX2 functions so that the combination of an S-100 backplane, S-100 Z80 CPU, and S-100 VDP.
I envision such a board to be composed of SRAM memory, a couple of 8255 PPIs, a card slot plus whatever extra IO and memory we need. If anyone has detailed MSX2 experience and would like to help out on designing an S-100 MSX2 compatibility board to complement the S-100 VDP please contact me.
S-100 and MSX seem like a neat combination but no one has tried it AFAIK. Thanks and have a nice day!