He wants the Eastern Part of Ukraine which is mostly Russian.
He has stated in the past, that he would be ok if the Western part of the Ukraine, which historically belonged to the Austro-Hungarian Empire and Poland, to become its own State free to join the EU and NATO, with main part of Ukraine, including Kiev, to be a neutral state.
I think this solution is the way to go.
An arrangement similar to the one you outlined might be the kindest thing for the people living inside Ukraine’s present borders, but we will keep this thing going, smoldering, for as long as we can. It’s all about keeping NATO relevant.