I think Ukraine should demand more than returning to the pre-invasion state. I don't know exactly what, but it seems like they should shoot for some verifiable changes in Russia's government, laws, military, or the like, and tie them to milestones for sanction reduction. If nothing else, that might help anchor negotiations in Ukraine's direction.
What if the west is certain they can take down their land based launch sites? What if they only need to concern themselves with the submarines? What if the west knows where those are? (Sonar has had huge developments 1990-$NOW) What if sonar technology has developed to a point the west have a fix on 50% of Russian subs? What then?
MAD only works if MAD means MAD, not if MAD means 50% assured destruction... The loss of life, wealth and security if one side of this insane pact ever lets down their part of the deal...
Anyway judging by their performance in Ukraine, I'm not convinced they have enough shit left in them to reach a fan. Who's to say their nukes work any better than their air force?