Russia has the most land in the world. People living in Ukraine and elsewhere who would rather live in Russia should just move to Russia. If it's too expensive then I'm sure Ukraine would happily pay the full costs of moving for anyone wanting to leave.
If Putin cares so much about them he should offer free tracts of land to people living in Ukraine who want to live in Russia. It's a much more peaceful way of resolving this.
Note I am NOT advocating forced relocation. It would be up to individual ethnic Russians whether they want to go live in Russia or stay at home and live in Ukraine or what ever other bordering country they are in.
It is not so easy as just packing up a moving. Many people believe that the Ukraine, and many other parts of Eastern Europe, should belong to Russia due to being historic possessions of Russia. And the majority of Ukrainians, especially in the Crimea, are of Russian descent.
Also, people are not just willing to leave their homes. This sense of nationalism is not to live in Russia, but to want to be a part of it... In their own land. Yes large swathes of Ukraine wish to be independent, and Putin's annexation of Crimea was less than ideal, pro-russian nationalism still exists.