Peoples immersion won't break for Protos vs Protos or England vs England. Ageof... Serries, Cossacks, Tzar, Rise of Nations and all RTS have mirror matches.
At some point you got to ask yourself as a company: Am I making games for "WW2 nerds" or strategy lovers?
I guess I have to quote from myself again.
Except that Relic already made Mirror in CoH2 beta and the game rate went down extremely quickly. Luckily they have realized thing before it's too late and fixed it up.
Your mention of the games are not comparable to CoH, not even a single bit, especially when it come to reality immersion. I play many RTS games more than just what you said. And to this day, nothing has surpassed CoH yet. Especially the original.
Edit: Oops, it seems that this go off the rail. Please open another topic, add the poll if you want to discuss further about this.