This narrative is more interesting: it takes Russian justification at more or less face value, but links it to Putin's dreams of Russia's glorious return to dominance and a special place in World Politics. It takes it's cue from Putin's famous remarks on the old Soviet Union:
Above all, we should acknowledge that the collapse of the Soviet Union was a major geopolitical disaster of the century. As for the Russian nation, it became a genuine drama. Tens of millions of our co-citizens and compatriots found themselves outside Russian territory.
Putin is here motivated not by blind cost-benefit analysis, but more like a romantic longing for the old power that Russia held for so many years. Often, this is linked more to the 19th century then the 20th; to the sort of glorious imperium once ruled by the czars of old. Here, Putin saw he was losing Ukraine, the kindred people to his Russia, to the west which has scorned Russia so.
This Putin is more irrational, more devoted, and less movable. He will not under any circumstance disengage from Ukraine totally; the costs to him would be too great. The barest minimum would be strong influence over the new government, but he would likely want to settle for much more. Here, invading the east of Ukraine or annexing Crimea are far, far more likely, and even the whole of Ukraine is not impossible. Economic sanctions and diplomacy are almost irrelevant unless he thinks he will win enough, and he doesn't. The idea of Russians, ethnic Russians, the people he governs, would be taken by the corrupt west is too much. He will not let the west win here, so close to home; how could he imagine himself the leader of a new Russia if he can't even keep Ukraine under his wing? Letting Russian people turn their back on him, he won't let it.
The positive aspects is this Russia will concede to anything as long as protects it's bases, is far less happy about alienating the rest of Ukraine, and more likely in the long term to fail (sorry pro-putininites, but it's true). The negative aspect is he is more likely to attack, more likely to conquer, and more likely to disregard the west