Why does Putin need Ukraine? As I mentioned above, there is the Eurasian Economic Union. I know some critics think it's too early to start calling it U.S.S.R. 2.0 but in light of Putin's recent actions, I don't think it's that far fetched. At any rate, here are some facts and info that help bolster the idea that Putin wants Ukraine like a fly wants poop!

"Sergei Strokan, a foreign affairs columnist with the Moscow daily Kommersant, argues that “Russia is really desperate, because Ukraine is the major trophy in Putin’s Eurasian Union project. That’s what leads Putin to pull out all the stops in the race to win this.” -imrussia, Aug 13th 2013.
"Russia experts have always considered that country the crown jewel—and even a necessary anchor—of any successful version of the Eurasian Union. “If you have Ukraine, the Eurasian Union moves a little further west, and puts it right on the border of the EU,” said Hannah Thoburn, a Eurasia analyst at the Foreign Policy Initiative, a Washington-based nonprofit. “Russia desperately wants to have Ukraine.” -The Boston Globe, March 9th 2014
"
"Given how much it appears to worry his allies, it might be surprising
that Putin would have played such a strong hand in Ukraine last week.
But that, say many observers, suggests just how much he has invested in
this idea. Ukraine—with its steel mills, coal plants, bountiful
agricultural resources, and massive population of 46 million people—has
always, according to Russia experts, been key to Putin’s vision for the
Eurasian Union." -The Boston Globe, March 9th 2014

“Ukraine is the big one,” said Alexander Cooley, a political science
professor at Barnard College who studies post-Soviet countries. “The
others are small and weak.” For this reason, he said, the success of the
Eurasian Union “hinges on Ukraine’s participation and cooperation.” -The Boston Globe, March 9th 2014
How much proof can you provide that Putin doesn't want Ukraine?

There are far more articles about this subject. I do find it odd that it gets little media coverage considering the literal obvious implications it has.