Twelvefield, I'm afraid I don't think we can do anything about this. It seems to be a preference more than anything. I'm sure if we changed it, we'd get plenty of people saying "Why is this defaulting to 'NYA', it's just one more step I have to take to make it 'NYY'!"
Granted, this is just my opinion, but I think it's somewhat more likely that most people playing a MLB-style league would prefer NYY, as that seems to be the standard used on ESPN, and most other newspapers. There are probably more people out there that either want NYY, or don't care either way, than there are people who hate the Yankees as much as you do.
I'm sorry if that wasn't the answer that you wanted to hear...
