First off who are you building this for, you need to establish that first or your wasting your time on design altogether.
You, your wife, you kids etc. that all plays into the design. Once you establish that then our critiques won't even matter.
I don't disagree with the design as in some cases simple is just better.
Marquee (overrated) especially for mame cab where you end up putting a stupid name on it that nobody likes.
Standing up playing against a wall IMHO is no different than standing in front of a real arcade, your standing regardless and playing a game, not sure who looks to the left and right of the machine during game play

This biggest issue with these wall mounts is maintenance with a floor cab its literally turn it around or access via coin door, with a wall design you have to take it off the wall, make sure you dont rip power cord, lean it up against something then work on it.
Another issue is space, what you gonna use to run it, and i see no speaker placement.
I also dont foresee you yanking this thing down on different levels of cleats, that will get old really quick.
All I can tell you is build it for the long run and not for the immediate need, at the end of the day it will probably be just you playing or it will sit and collect dust until you have company, and half the time they could care less to play they just want you to turn it on cause it looks cool.
I also agree in putting the cart before the horse, if your wife hasnt bought into it, you're going to put a piece of ikea on that wall.
Your best bet may be to get a pandoras box and just pull that out when you feel like playing.
Oh and if you are building this for you we all know it wouldn't look like your first post not one bit, build it/design it for the person thats going to play it.