Hmm......looks like I'll be using these TV's after all.
240p firmware via composite is available for the raspberry pi to use with Retropie. Besides for a little bit of dot crawl, I have seen YouTube vids and the image is rock solid.
I'll be using this though :
www.retrotink.comThis kid built a hat for the pi that outputs 240p via either Component or S-Video. The S-Video looks great.
So there is finally an emubox solution that can you can hook into a curbside TV and get a progressive picture. Granted it can't do all the custom resolutions for MAME but console wise from the Atari 2600 to PSX this is a great alternative.
Someone needs to make a small converter box like this now that's geared towards American CRT televisions that's compatible with PC. I guarantee they would make a lot of money.