Elegant and Simple: Ukraine should sell Crimea to Russia, ala The Louisiana Purchase or Alaska aka Seward's Folly.
The Ukraine would sell Crimea for a large enough sum to:
- recreate necessary naval infrastructure further up the coast.
- resettle anyone who would like to leave Crimea and provide good housing, jobs, etc.
- develop large alternative energy projects to reduce their dependence on Russian oil.
- help stimulate Ukraine economy.
Russia would get:
- access to its centuries old warm water port. This is very important to the Russian psyche.
- Russia shows off its economic might by buying the Crimea.
The inhabitants are given the option to stay or resettle with resources.
All legal issues are resolved through the sale.