This is based off an eariler project I was working on last spring but was cut short by my summer classes and a trip to London.
This is sorta a mix of a GSTK feudal RPG and a grander alliance type game like the Swords of the east based stuff set in Early mideaval Russia.
So the core organizational structure is the Realm(kingdom is too tight of a term) of the Kievan Rus. You have 4-5 semi independent princpalites(Roughly Novgorod, Vladimir, Polotsk, Kiev, Volhinya/Ruthania) which are ran by a king who is the most powerful prince. Now in theory, the princes owe fealty to King, but in reality, its more a balence of power poltics, as all of the Princes should at least through the male line have Rukid blood and be able to claim the throne.
Also, at the level below the princes, players can play as most any polity inside the borders of what would now be concidered the European former soviet union, be that a Bulgar Khan, a Khazar/Pencheg or Finnish Chief, Feudal vassals of the Princes, or leading merchants of major cities.
Keep in mind at this time, given the early time period and lack of laws and regulation like in the later feudal system, rulers in Russia are at this time absolute, and also there is not very clear definitions of what is legally a certain territory or ranks, instead, aside from the seats of Princely towns being part of their rulers patriomony, the only real things on what is held by a specfic ruler is by that rulers military strength and the personal relationships of the ruler with lesser powers
A good way of thinking of teh poltical structure of Russia at this time is like a wheel with the ruler at the hub and his vassals relationships primarily going to him instead of to eachother or in a pyramidal structure like in later periods in western Europe. Also, unless you had the military strength to fight your ruler, or you were an elected head of a merchant city or a tribal cheif, vassals served at the pleasure of the Ruler, or Vzhod