Whether a player makes an "FA only" city or not, is not the problem. It's that they do so against the rules IF they do it with an alt city. And most do, I believe (could be wrong, but does it make sense that you play only every 6 weeks for a week and are absent the rest of the time becuse you set your city up for the FA only?). In any case, if a player is using his/her alt for the city, they are breaking the rules. Alts are not allowed. But of course, like all "laws" if you don't enforce it, you are implicitly granting the right to break it. And Inno never had enforced the "one city per world" rule.
Now, before anybody gives me a hard time here, I could be wrong. Maybe Inno does allow multiple cities in a world. I'm only quoting what I've heard said many times, so I may be wrongly informed. If so, then the "FA only" city would make sense as, why not? If you like winning the FA, it would make sense to make a city for doing so.
In any case, all this reminds me of my African friend who played international soccer when he was a young man. Made the "all African" team and travelled the world. The thing is, he has always maintained that his talent level was not that high, but his desire level was. He desired to reach a certain level and he made the sacrifices necessary to do so. The FA seems to me to be the same sort of thing. Some people will make the sacrifice to get to the top spot because it's worth it to them, including using alt(s) specifically built to win the FA. Others of us, including myself, will be content with what I think is the real "1st place" somewhere between 4th and 10th. If you watch the progress of an FA, that's where the real competition seems to be.
AJ