Well, I had this idea a long time ago... but here goes...
Some arcade games monitors are mounted facing upward, using a mirror to point them twords the player. Some other arcade games used a police style 2-way mirror, and had artwork lit up behind the mirror - so that it the art apperas to be behind the main display, and creates a 3d effect. (discs of tron)
You could mount 2 monitors... one facing up, and one directly forward, both seperated by the 2way mirror. If you choose, both could rotate.
These are some types of configurations you could do:
Arcade / Vector Arcade
Arcade / Arcade (one vertical, one horizontal no need 2rotate)
Arcade / PCmonitor (so one can use windows clearly. Also, you could project artwork through the rear mounted pc monitor, and make those custom 3d display effects - which is why I came up with the idea
Also, you could place 2 side by side for dual monitor display - if mame ever supports it... that or networked gaming via 2 pcs.
Also, another way to rotate different displays... you could make a cab thats top section rotates horizontally. Place all the monitors you can fit on this rotating table, and simply rotate the correct monitor to face you controls. (though you may need some sort of magnetic shielding surrounding each monitor?)
The downfalls... well, its been said that the 2way mirrors that have the mirror coating on the front side of them are pretty expensive. Ive yet to go to a mirror place and ask though.
The rotating monitor table may eat up a good chunk of space.