On that note, in the longer term, I'd want to look at whether the VGA_I2C board could support all 3 buttons on a Sega Genesis controller since there is a lot of commonality with the 2600 joystick. This greatly expands options for supportable arcade games.
I see that +5V is on a different pin on the Sega controller, so I suspect not without some rewiring to fix pinout, and doesn't look like more than 2 pins is plausible, but still better than 1.
I did, but unfortunately killed it by hooking up the wrong power supply with reverse polarity to it. I have enough experiments on the Pano G1 for now.
Once you're ready to move back to the G2, let me know. Since you're actually doing something with, I'm more than happy to give you one of my stash.