Second bunch of observations - digging deeper, I've found some fundamentally wrong things about Russian setup in 1066.
1) Religion.
In 1066, Russia is shown as a christian monolith - nothing can be farther from truth. Despite the fact that all princes by that time were christianized, there were vast regions where christians were still a minority. List of christian provinces that should be pagan instead: Vologda, Bryansk, Kolomna, Ryazan, Moskva, Mozhaysk, Galich Mersky, Gorodets, Nizhny Novgorod, Suzdal, Vyatka, Rostov, Murom.
2) Which brings us to another important entity -
the Vyatichs. A staunchly pagan and independent tribe that occupied much of central Russia in 1066. This warrants a duchy- or kingdom-level tag for a tribe of Vyatichi, Russian pagan, elective law (chronicles say there were "no princes" in Vyatich lands, and leaders were elected). Provinces: Moscow, Bryansk, Kolomna, Murom, Ryazan, Nizhny Novgorod (?). Also, while Vyatichi were of clearly slavic descendance, these currently Mordvin provinces should get Russian culture: Nizhni Novgorod, Ryazan, Murom, Kolomna.
3) Cumans - to stimulate historical expansion, their ruler should be given claims to Pecheneg provinces Belgorod, Olvia, Oleshye, Peresechen. He also should have a younger brother, Sugr - 14 years, martial education.
4) Characters:
4.1) Simon the Varangian. Donated all his riches to Kievan monastery. Born around 1035, suggested traits: Crafty Merchant, generous, zealous. Suggested culture/religion: Scandinavian orthodox. Suggested province: Kiev.
4.2) Leontius of Rostov. Later canonized by Russian Orthodox Church, spreaded christian faith in then-pagan Rostov. Born 1016, died (martyred) 1073. Suggested traits: Scholarly theologian, amiable (was very tolerant to pagan clergy).
4.3) Kicha of Rostov. Main rival of Leontius, head pagan priest of Rostov. Born around 1022. Suggested culture/religion: Russian pagan. Suggested traits: hostile, deceitful, sceptical (tried to trick people into burning christian church by talking from inside Veles' statue). Has a son, Kruglets, (6 years in 1066, ecclesiastial education), who converted to christianity.
4.4) Arkadiy Novotorgsky. Bishop of Vyazma. Since Vyazma is in the demesne of Vsevolod prince of Pereyaslavl, should either be in his court, or given Vyazma as his bishopric. Fanatical priest, zealous, (schizophrenic - or at least reported to be in his childhood, I guess he wouldn't become a successful cleric later if he was clinical).