Here are the bells and whistles that I would like to include in my cabinet design, in order of priority.
3 monitor system. One for Game Play; One to Mirror the Game Play for people watching; and a Ultrawide Monitor for the Marquee.
Marquee that does not just show static images.
Rotating Monitor. Could be problematic for the monitor that is mirroring. (Optional)
Yeah, I don't see a way to pull this off without also having the mirroring monitor rotate.
You could make it also rotate, but IMO the added hassle of doing that, the added hassle of trying to get emulators to display the same thing to two monitors while displaying something different to a third, as well as the extra GPU power that will be sucked away, makes it just not worth it.
Do that many people really want to watch other people play?
Cool LEDs and External Lights. Additional Option - Pulses to the game sounds.
Easy enough to do with the standalone LED strips from amazon or ebay.
Personally I think it's tacky, but have friends that love it.
swappable control panels
I can dig it.
For the monitor, I'm using a 27" 16:9 screen and like it. It gives you around a 24" 4:3 image.
Just be careful about the viewing angles if you're going to physically rotate it.
Most monitors aren't made to be viewed from the bottom, so they appear darker from that direction.
If you have a poor bottom viewing angle, either P1 or P2's side is going to appear darker than the others.
The majority of vertical games require the monitor to be rotated counter clockwise.
It's not a big deal with MAME since there are options to rotate it whichever way you want, but it helps with other emulators and the taito type x games if you have the monitor rotate that way.
I've got no recommendation for a front end. I use Mala which has awesome support for rotating monitors, but it's no longer being maintained.
So using it with the latest versions of MAME require a bunch of workarounds.
For the GPU, it depends on what emulators you plan to run.
The more you spend the more games you can play, but it is a case of diminishing returns.
MAME doesn't require much of anything. Demul requires DX11 and a decent level card (at least 60 series...460,660,860, etc...70 series would be better).
If you have a bleeding edge processor and GPU, you can play PS2 games.
On the processor, go for the highest speed you can afford (at least 3GHZ or GTFO).
4 core is fine, you won't get much of a boost running more cores than that.
The cabinet can be turned on and off via a remote.
Why? Seems like a pointless feature to me. One more remote to keep track of.
Now if you had a game room where every device in there booted up with the push of one single button, that would be useful.