We must think the same. I dug out my RP the other day and installed Retropi and in process of getting that set up. I was also thinking how I can make it portable with screen etc.
Remembered I had an old MacBook (not working) and thought - pull the guts out of it and use that as the case.
Well I have done that today but not moved on any more - yet.
I am calling it an "ApplePi"
See what goes over time