I was trying to use my old (2012) game client with Island Rum and its updates, and it kept either throwing errors or hanging on the login screen (I also tried downloading the game client from scratch that way). I downloaded your version of CoH as you prescribed, went through all the security protocols for High Sierra, and also installed the X11 emulator you suggested (required a reboot to start working). After that, Tequilla works great in the emulator and the only weird thing about launching the game for the first time was the 1080px screen default (easy enough to fix in settings).
Thanks so much.
I was insanely happy playing the game today, reincarnating my old ice/mace tank and getting all those free powers from the P2W vendor. So much fun.