About Russia - Rus' that respawns as Ukraine/Belarus and this "Central-Asia-civ" with Tatarstan/Bashkiria in historical/core.
Also for Eastern Europe flavour can be added respawn of Byzanthium as some generic Balkan civ (no UU, no UP, state name depends of the capital - Croatia, Serbia, Bulgaria, Bosnia, Romania, Albania or even International Free Zone)
So, Rus/Ruthenia/Ukraine and Muscovy/Russia/USSR.
Rus - spawn 860 in the Kiev, 2nd settler near Novgorod.
UU - Cossack (vanilla) or Ushkui (scout with attacking ability);
UB - Ostrog/Detinets (replacement of walls, cheaper but without production bonus from stone).
UP - Power of Amber road: units can use rivers as roads.
UHV:
- Raids of Svyatoslav: kill 15 enemy units before 1000 AD
- Shield of Europe: do not lose any city to Barbarians or Mongols until 1500 AD
- Mother of the Russian cities: acquire X culture in Kiev in 1600 AD
Core - Ukraine, Belarus, before Renaissance also NW Russia near Novgorod
Historical - NW Russia, east of Black sea coast (Kuban and southern Volga), probably - Klyns (some regions on the Southern Siberia and
Far East).
Names: Rus' peoples, Grand Duchy of [Kiev|Novgorod|..], Ruthenia (after the Renaissance), Ruthenian Empire; Ukraine/Belarus (depends of the capital's location) after the respawn.
So, current Russia:
- spawns at the 1300 AD in the Moscow as `Muscovy peoples`, later Grand Duchy of Muscovy etc... At initial spawn doesn't flip anything, player needs to conquer core manually; if player selects Russia, Rus probably shouldn't spawn, only strong indepenent Kiev.
- UU: Katyusha (earlier modern artillery) or T-34 (cheaper tank)
- shift its core eastwards, to Volga region.