This looks really cool. I'm restoring an 80's SEGA candy cab with a CRT and have been trying to figure out the best way to most accurately utilize the 15khz display in it. I tried bit-banging from a Raspberry Pi's GPIO, but landed on using an AMD GPU with the capability outputting a usable signal. This also looks like something I want to toy around with.
I took the easy way out, similarly - got an ArcadeVGA pci board, which is basically an ancient Radeon that supports 15khz well. I drive it with a groovy arcade Linux install and a pc2Jamma adapter that maps jamma buttons to keyboard input and VGA to the crt.