1. Crimea under joint or triple authority, its local administration based, not on majority voting, but on multi-optional, preferential decision-making.
2. All other pre-2014 borders to be recognised. Russian forces to be withdrawn from Donbas, etc., Ukrainian forces from Russia.
3. Mitteleuropa or Middle-Europe to be neutral: from Finland and the Baltic States, via Poland, Slovakia, and Hungary, to Ukraine, Moldova and the Balkans, all to be non-nuclear and not in NATO, but if individually desired in the EU.
PS. In Ukraine's 1991 referendum, every oblast voted for independence by 80% or more... except Crimea, 54%.