Hi.
1. Did you prefer some components for hardware platform or i must propose it to you. I mean WiFi module, graphic accelerator, sound accelerator etc.
2. Did you need games loader and games?
3, What manipulators you want to use and quantity? It can be parallel connection(like NES) or sequence(next manipulator connect ot prevoius like Panasonic 3DO, N64).
4. Did you need expansion port for connecting other hardware for gaming?
5. Games must be placed on SD cards or something like cartridge?
6. Did games can be saved and restored?
Also after you testing this system as Arduino based i can make an original pcb for this system.