I'm not a fan of cocktail cabs, but I like that you've tried to get some angle on the screen so the player is looking at it more than across it.
I'm weird about sitting too far left when playing one player. Do you plan on playing this by yourself or with a Player 2 most of the time?
What are all the button holes in the center for?
The angle serves two purposes. offset the vertical viewing angle so it's more square on to the players and also help reduce any reflection element of the glass top.
You are right in the horizontal offset will exist for either player. I thought this was not much different to an upright 2-player cabinet where either player is slightly offset from the screen. I've done a test run using my daughter's adjustable drawing table and it's not too bad. I've got a 20" 4:3 LCD display I'm using. But yes, horizontal viewing angle is a disadvantage here compared to the traditional opposing player cocktail cabinet.
A few of my kids are interested in this. Many of them have seen MAME but many years ago. They play PC games together and I have 4 boys who like fighting :-) so hopefully they give it more punishment than I will :-) so a 2 player optimised cabinet is ok with me.
The extra buttons in the middle are (going across):
Start 1 / coin 1
Exit / esc (top), pause (bottom)
Start 2 / coin 2
I'm also considering putting a graceful shutdown button for the Raspberry Pi somewhere (eg. underneath). Might label it the "panic" button :-)
The hole underneath is for the coin mech. I'm going to put speakers side by side. Unsure if I'll buy coaxial or recycle some others and design a crossover.