Agreed. Personally I would like to see following split: Novgorodian in the north, Muscovite in the east and Ruthenian in Lithuanian areas. Then by 16th or maybe 17th century Cossack culture appears in areas taken from Tatars in the south, Ruthenian splits into Ukrainian and Belarusian while Muscovite and Novgorodian unite into Russian.
Maybe rename Novgorodian to Pomor ? https://en.wikipedia.org/wiki/Pomors as they were considered a highly divergent bunch of Russians.
Ukrainian and "Belarussian" should split only if a border exists between these two areas for say, 25 years.
Muscovite and Novgorodian also should unite only if one country controls both cities for say 25 years. If the area isnt unified politically, the identity of the people will develop and "Muscovites" will be Muscovites with heart and soul.
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