It will be downright cold in Crimea if the tensions escalate. Their gas for heat and cooking comes from a pipeline that crosses Ukraine.
Putin's adventure may turn into a real mess if you look at the history of past Russian and Polish attempts to rule Ukraine.
Imperial Russia ruled Ukraine for 350 years, and after that the Soviet Union ruled it for another 72 years. No big deal.
I am surprised that Putin only wants Crimea. There is much larger geographical area that wants Russian rule.