Ultimately Russia would like a land corridor to the Crimea.
I’d suggest more of an interest in a corridor all the way to Transnistria in Moldova. That would deny Ukraine access to the Black Sea and regain the major port of Odessa….
A matched pair, so t9 speak, with a move to take a land corridor back to Kaliningrad and it’s warm water Baltic port.
https://en.wikipedia.org/wiki/Odessa
https://en.wikipedia.org/wiki/Transnistria