Microswitches mounted to the Eject and Reset buttons so that they might serve a purpose, and USB jumpers mounted to the controller ports. (I am going to need to shorten those at some point.) A 3rd USB port is planned to be mounted inside the cartridge slot, but until I can get that planned out, the USB in controller slot 2 should work just as well.

If everything goes according to plan, this is all the cosmetic differences there will be.
I have ordered a Raspberry Pi 3 Model B to use inside this thing, and have already downloaded everything that I should need.
...It just needs to arrive...