So, first of all: no, the "number 9 rule" is not an issue, since it's really just a joke (which we keep if we can) and not a rule. We said before that this would not stop us from making a game in a setting we would like to explore.
However, 1944 or WW2 in general as an era is not something we're very keen on. It's a very dark time, not many positives here. That does not fit with our more light-hearted approach to theme and setting.
Quoting from your original post: "it would have the largest sea battles, coolest ships, imperialism, multiple theaters, resource wars, amphibious assaults.." it also sounds to me like you're looking for a different type of game. Wars and combat are a part of Anno, but would never be a major focus. So, that's another point against the setting. It's not really a time of building, but rather one of destruction.
Highly unlikely that we'll ever create an Anno game in such a setting.