I spent some time over at The Dignified rant and like his solution for the Ukraine crisis. The Ukraine has leased Sevastopol naval base to Russia until at least 2040. Why not just sell them the city outright and trade that for Crimea and assurances of reasonable access to energy going forward? It's an interesting variant that I haven't seen elsewhere.
It's rewarding aggression, true, but I don't see how aggression is going to be rewarded any less in any other reasonable scenario.