My next project will be looking at modifying the PiGRRL Zero Advance and using a regular Pi 3 and the new Hyperpixel 4 to possibly have a really nice high resolution screen on a faster project. The Pi 3 should be able to drive Nintendo 64 and Playstation games, so I'll be looking at adding a joystick and another set of shoulder buttons and possibly a six button (similar to Sega Genesis configuration) layout.
I also want to do a variation of the PiGRRL Zero Advance project that does a Pi Zero and a really tiny screen making a micro option. I've seen some cool versions of this, but they seem pretty difficult to build without putting the whole system on a board. I would prefer to still make this something you could put together yourself.