did you see meltman's WIP (link)
It looks very stylish and is 4-player.
That could be one advantage of having the screen at 45° to the corner with controls all around, but...
If you don't often have 4-players and you play vertical and horizontal games it might be better to build a rectangular cocktail so that you can play either screen orientation without rotating the monitor. I use my generic Dynamo cocktail like this; one controls set for horizontal games and one for vertical games; just no head-to-head because it's in the corner
Meltman's deal is bad ass, that's very similar to what I had in mind, with some changes.
I can't do a cocktail game because the single request my wife had for the game room was that we get a pub table (I have no idea why this is so important) and she wants the table up high with 2 high back swivel barstools. Since the room is filled with my big upright arcade machine, lots of neon beer signs, pool table, LCD TV, darts, etc... all of which she had no input about, I told her I'd go ahead and do the pub table deal instead of another video game. So now I'm trying to work another game into the pub table deal so we can both get what we want.

I mainly only play the classic arcade games (I'm 36 and can't comprehend the newer fighting games, I just don't get it) my MAME machine is geared towards accurate play on the classics. So I don't have the ability to play head to head 2-player games. it would be cool if my pub table/cocktail could accomodate 2 players.
I'd like the control panels to be recessed so the table top is flush and made from oak with a smoked tempered glass square insert set in flush with the top that the monitor is mounted under. The "game" portion of the table wouldn't interfere in any way with using the table as a table, but it would still be easy and comfortable to play.
As far as monitor configuration, I guess it would be a compromise because I'd have to mount the 19" PC monitor one way or another. I'd mount it horizontal and my verticle games would be pretty small I guess on a 19" horizontal monitor. But I have a machine with a 27" monitor if I need to play verticle games on a full sized monitor.
For controls, I'd like a left and right control station each with the 8-way & 7 buttons. Then in the center I'd have a 4-way with maybe 3 buttons each, a trackball and spinner . That should allow all of the classic to be played with the center 1-player station, and the 2 outer stations would be used only for head to head games and games that require an 8-way joystick. Plus a P1 and P2 start buttons, P1 and P2 coin buttons and a pause button.
That's 3 joysticks, a spinner, a trackball and 22 buttons. If the P1 8-way and the 4-way share keys, and if the 3 buttons in the center shared keys with 3 of the P1 buttons, I'd still need to map 19 buttons plus 8 joystick keys. That's 27 inputs on an Ipac, which should be just right for a IPAC2 with 28 inputs.