First of all I LOVE all your other mods. I just bought the FM21 and got all of them again, like last year.
But with this one here I have one complain. I don't know if it's that big of a problem, considering I can pretend it's not the language but the culture in the new city/region like you mentioned in "4." in the feature list.
But here it is, just for information and in the end I won't think it would be a "gamebreaking" obstacle and I will start my first save with it regardless.
I'm from Germany. And almost everyone (maybe 99%) here speaks High German. When they are at home with their families they would maybe speak their dialects. But when a for example in Hamburg born kid moves to Munich, Bavaria, he would only have a minimal language problem while integrating. There are some words he might not know, but most of the Bavarians would know the High German word for it.
High German is the German dialect that's taught in school. Well, it's not a dialect, it's THE German language. High German is German.
Yes there may be some Bavarians or Saxons who have such a strong dialect that you can't understand them. But they would adapt when talking to someone who doesn't know the dialect. But mostly that would be some old famers (50/60+ years) living in the rural area or highlands of Bavaria or former old DDR citizens from Saxony who never learnt High German in School.
But you could say that every for FM relevant German person could speak High German. That young boy from Hamburg I mentioned earlier could have some communication problems while talking to the 70 year old lady down the street but at FC Bayern Munich they would speak High German.
Not one in the 2000s born youth player would have a hard time integrating into his new club because of the dialect. Yes a kid from the rural area moving to a big city, but not because of the language, but rather because of the fact he's living in a city now.