>> fact that the large majority of the population in Crimea

It's not a fact but propaganda from RussiaToday.

How about to go the Russian way: put troops there, make them do a referendum, be sure people see guns and Ukrainian flags. Anyone who will not make a Ukrainian passport soon will be deported or imprisoned. They are ok if Russia do it - then once more will be also accepted.

>> Maybe you're more optimistic?

There are €300b of frozen Russian money, also a 10% reparation tax on oil export could finance the rebuild of Ukraine.