I setup basic RetroPie with a monitor and keyboard, but when I went beyond that I discovered a big learning curve with no prefab solution, so thought I would make one. Since no one wants exactly the same thing, or may want to fabricate some, or make custom parts, it is extensible.
Features are:
1. Open Hardware
2. Inexpensive
3. Buy what you what, make the rest.
4. Hardware is off the shelf, laser cut, 3D Printed, or Home Depot.
5. Portable
6. 2 Player