I don’t agree with the ‘grinding war of attrition’ part. I guess it depends on how big of a bite from Ukraine they take.
Would Putin be satisfied with a larger part of Ukraine, or will he stop only when he forces the whole country into a revived version of the USSR (perhaps along with Belarus)?
I agree...the eastern regions which have already seceded from Ukraine could be folded into Russia without much difficulty, and my guess is this action would prompt additional eastern regions into secession.
The big question then would be whether or not a move by Russia into eastern Ukraine would push Western Ukraine to secede from Kiev, effectively splitting the country into three parts.