I've just completed the design and feasibility phase of this project.  I found myself with a spare 43" 4K TV and was thinking of something to do with it.  Turns out, with nVidia drivers, I can set the resolution to 2160 x 2160, and rotate it, making a perfect, 28" diagonal square smack in the middle of the display, which is awesome in that it gives equal footing to vertical and horizontal games.  I designed a cabinet around this quirk in sketchup.  Just today, I did some mame tests to see how it would look.  Turns out, kind of amazing (that's a lot of pixels for HLSL to do its magic.).  I did a lot of fine tuning on the cabinet, but will start looking around here for tips before taking the plunge.