Interestingly enough, I realized as much today - I do, in fact, have A2:CO functional. The splash screen and logo still say AO, but I can run A2 campaigns from it. So, while steam won't recognize CO, the standalone .exe does.
for some reason, i thought this was supposed to make steam recognize CO. i would have preferred that, because then i wouldn't have to do this "integration" kabuki dance on every machine i may use. but... it works. so whatever