How about a re-jig of the borders in this area? Return Western Galicia to Poland, Sub Carpathian Ruthenia could become an autonomous protectorate of both the Czech Republic & Slovakia, Die Bukowina & Moldova to be incorporated into a Greater Romania.
A plebiscite should be held in what is left of Ukraine to decide whether the remaining population wish to join the Russian Fereration or form their own independent country.
Whilst we are at it Königsburg (Kaliningrad Oblast) should be governed as a free trade entrepôt directly by the European Union and Russia should be forced to cede Vyborg, the Karelian Isthmus, & the Petsamo region back to Finland.
(NB I have consumed a few Aspall Premier Cru ciders at 7% ABV

)
Russia should then be told that Eastern Europe if off limits from now on in
but that to compensate it can have a free hand in Central Asia - Russia's role in
weltpolitik is the protection of Europe from the onslaught of the
Asiatic Hordes!
Remember throughout history in this area borders & boundaries have come and gone, in general this did not affect too much the actual people living on the ground so to speak as all that really happened was a change of monarch, a new governor, and a new flag. It was only with the rise of nationalism in the last century (esp. in conjunction with fascism & communism) that the great genocides of Eastern Europe as well as the major population shifts have taken place. It appears that these upheavals have not yet fully resolved themselves in Ukraine - let us hope and pray that these current unrests are resolved soon and that, God forbid, they do not escalate across any neighbouring borders.
I can recommend the following books:-
Borderland by Ann Reid; God's Playground by Norman Davies, Historical Atlas of Central Europe - Magosci.