Along the lines of Yugoslavia, could Pan-Slavic movements have created a West Slavic state (Zapadoslavia) and East Slavic state (Vostokoslavia)?
The East Slavic state would probably unavoidably be dominated by Russia, but depending on how liberal it is, it could have autonomy for Belarus and Ukraine. Maybe Cossack, Baltic Russian/"Novgorodian", or Siberian regional identities could split up Russia's influence.