I think it's time for small update as we are moving forward on this project.
The Multi PCB has as usual ( similarly to CPS2 ), a microSD Slot, LCD display and mounts in place of the B Board. All games are supported natively without modification. One of the features....and here comes a good suprise, the multi includes the C board on it! No need for C board with this multi.
We are exploring, but that's still in beta phase ( don't be later surprised if we say that we won't do it ), we are trying for the multi to have natively support for other types of sound, starting by letter Q