I for one am both historical minded, and think it would be FUN (the point of the factions!) to have other period correct factions that could have possibly fought in the Civil War. I don't get all of the massive hate, these will more than likely be FUN ROUND factions, not "Alright guys let's have the Mexicans fighting the English.
It also sets up the opportunity for some more historical events outside the Civil war, for example the French military colonization of Mexico in the 1860s, or even some far-stretch Mexican War themed battles. They're there for the fun and you guys are just being sour puss' because it's not the union or the confederacy! I mean really. They developed the content for US to use and play out our OWN discretion, it's not like Hinkel is saying "PREPARE THINE BUTTHOLES FOR ANGLO FRANCO MOD!".
I mean really.