As someone who has purchased the ' 5th Edition by FFG, I agree a MU* is hard, the culture's 'hard' rules are part of the draw, but culturally in MU* trying to enforce what the character would know via training and culture would be hard to enforce.
But it would be a lovely world to play in, if you drew from the wealth of 4th edition (extraneous information), but used 5e timeline & cultural reference) would be great.
The downside is that you have to have a good player base to keep the correct cultural feel, but I kind of love the idea of being able to sit and sip tea, or talk mystical philosphy.. or travel be a horse-girl (because you know Unicorns are best! But then so are the Crane)