In my opinion there’s a potentially big market for a modern flat panel display that comes in a 4:3 aspect ratio. A display which is specifically intended to be used with retro gaming consoles or arcade cabinets.
There used to be 4:3 flatscreen displays but those primarily served as computer monitors and only got as large as 20 inches, and they came with VGA or DVI inputs. As far as I know, flatscreen TVs for the living room always came in a 16:9 aspect ratio.
It wouldn’t be enough to just make a 4:3 display, this gaming TV would need a built-in upscaler (like the Framemeister) to enhance all incoming signals to fit the HD display.
I also recommend that the display breaks with the standard 1080i resolution, and instead offers a unique 960i display that would be tailor-made to host the majority of systems. Here are all the (pre-HD) systems and their native resolution, along with the multiplier needed to fit a 960 display:
Unfortunately the SNES and Genesis don’t fit the mold, so there would either be some stretching or a black border to preserve pixels. Atari Lynx and Phillips CD-i don’t mesh either, but who plays those? Overall a 960 display is a much better fit than 1080 for all systems.
This TV would need all the connectors of yesteryear: RCA, Component, S-Video, and possibly coaxial for systems that used RF switches. Maybe SCART as well, for folks in Europe.
EDIT: because this TV is exclusively for retro gaming, the remote won’t feature channels, playback buttons (pause, fast forward, etc), or number buttons. Just power, volume, and a bunch of input buttons. Maybe a scanlines toggle as well. Sure you could watch broadcast TV or Blu-Rays, really anything in a 16:9 ratio on this TV, but it would be letterboxed.