It would be 100% correct thing to do from a strategic point of view to
Eliminate (not just cripple and de-militarize) a rabidly anti-Russian regime once the Donbass and southern forces are defeated. As you and Wolfie said, whatever remaining weak force in Western Ukraine are unable to resist.
But...knowing Putin, he is probably be content with holding the east and South (
) and that is a strategic mistake. He cannot allow a crippled regime to exist, that just kicks the can down the road. I don't have much confidence he will go all out to eliminate Kiev, he might just declare victory after East/South (
) is conquered, which is unfortunate, since a NATO-backed crippled West Ukraine is still a thorn in future, no matter what a paper promise says otherwise. He should Go Big (or go home) is what I'm trying to say.