how about a combination Atari, ColecoVision, Commodore 64, compact set top box complete with cartridge slot plus SD card to load ROMS. it would be great if instead of how you did the combo console, if you could make it so you just use a switch (hardware or software, ideally a software switch) to switch between systems.
it would also be great if you could also show how to convert the stock controllers to either wireless or even USB. even better if you made a keyboard/gamepad combo.