Got a new proto in. Works great. Not too thrilled with the overall size, but I'm looking at some alternative mounting options. I have a feeling the bios socket on the MVS board will need an IDC ribbon cable/adapter to connect to this. Right now it's been tested on and works with 1F and 1B. Still no 1C support, and I have had some issues with the 1A boards. The 1A series uses a different chip than the others. Only thing I can't find are the card detect lines on the 1A, a similar problem to the 1C system.
Oh and this will work on the Neo Deck system. Though, I doubt anyone will mod theirs.
As far as installation difficulty, you're going to need to feel comfortable soldering to a SMD with a tight pitch and lifting a couple of pins. You'll want an experienced tech to do the installation. Depending on the board, a few traces need to be cut, a pin needs lifting and solder down about 4 wires.