The problem is NATO. IMO NATO pressing for a solution earlier would have just created a crisis earlier.

Also, I believe at this point that an agreement that Ukraine will not join NATO is necessary. We (the US) have shown the world over and over that we don't keep our word, but Ukraine giving Russia its word that Ukraine will not join a belligerent (from Russia's point of view) military alliance is (again IMO) necessary at this point to defuse war tension.

I agree somewhat that it is possible the Donbas joins Russia, but more likely Crimea and Donbas would be semi-autonomous regions of Ukraine. Similar in ways to Baskenland and Catalonia in Spain.