Sicilian, Bavarian, and Saxon would probably cover it as far as new cultures in Germany and Italy go. Enough to fracture it a bit and represent history but not so many as to go too far. Any more and we'd probably have to add Galician and Aragonese (maybe Leonese) in Spain on similar justifications.
But Bavarians and Franconians and Swabians didn't have that much problems together then with the Saxons in 1066. We shouldn't split German too much. They weren't that fragmented in this time. Saxon, Frisian, Dutch, German would be enough I think.
What would you break German into? What comes to the top of my head is Saxon, Hanoverian, Rhinelander, Hessian, and Bavarian... but I doubt any Germanic people see those as cultural differences as much as someone from Wisconsin sees someone from Illinois. Now, if Bohemia had been lazily listed as 'German' I think we'd have an issue.
This is a German split... And wouldn't make sense. Saxons and Hanoverians are the same in this time. Saxons were the inhapiters of whole northern Germany. And the Rhineland culture is also more modern. I don't like this list for this time period. If you split German massivily, it would be the Steam Duchy cultures. Swabian, Saxonian, Bavarian, Thuringian, Franconian etc. But that would be too much ingame.