I'll agree with Sean Mirrsen here. Russia will only do something, if they are given the excuse to.
What stops Russia from just saying they were attacked by Ukrainians or inventing any other lame excuse? Why they need and kind of excuse if their television will happily say any nonsesnse? That will be repeated by Churkin and Putin later
To put it simply, the Chelyabinsk Meteorite effect. Exactly when Russia took Crimea, exactly how it went down, nobody was ready to look out for it when it was happening, and all there is to see - for non-Russian non-government or non-military people - is only the aftereffect - like a crater from a typical meteorite. Ukraine right now is a Chelyabinsk equivalent. It's open to European and US journalists, and it's very much expected - due to the exact logic leaps you propose - to be in some shape or form attacked by Russia. Any sort of direct, unprovoked action by Russia is inevitably going to be reported, giving Russia/Putin much less capacity for counter-propaganda - so it's plain not smart.
After all why not get all Ukrainian military equipment in Crimea without firing a single shot and than attack? They already move our former tanks to Crimean-Ukrainian "border"
As above. Not smart. Bloodless commandeering of a fractured territory with overwhelming people's support both here and there is one thing. An act of war is something entirely different - if there's anything besides gay parades that the general Russian public is overwhelmingly negative towards, it's outright war.
Capturing Ukrainian Navy is rather senseless, most of that old ships have little to no practical value for Russians BUT should that vessels pull out they could be used in delaying amphibious landings along Ukrainian coast
Heh, now that I agree with, the "senseless" part particularly. I believe that those ships were seized as the exact same sort of preventative measure that had Ukrainian military units in Crimea forced into surrender. Ukrainian government is believed - both by the general public due to the "leaked calls" and other such things, and quite probably our government as well - to be capable of rash, un-thought-through actions, including surprise attacks and guerilla warfare using troops and hardware based in Crimean territory. Just as the massing of troops along the borders, it's meant to first and foremost guard the Ukraine against the Ukraine - an attempt to radically prevent attempts at armed opposition, so that it doesn't in turn lead to uncontrolled escalation of conflict.
Now, whether or not it'll backfire in the long run - we'll see, I guess. :\
There have been plenty of outhright acts of war - sinking hulks to block off a Ukrainian navy base and several towns' access to the sea, boarding ships of another sovereign nation, blockading and taking over military bases. It seems like Russia has tried a lot harder to provoke aggression than prevent it, what's incredible is that there haven't been any more serious incidents and kinda moots the "risk of rash decisions" argument.
Taking over what's essentially the entire Ukrainian navy seems from my perspective like deliberately weakening Ukraine's military capabilities, to make them more vulnerable and more susceptible to pressure. It's been done before, when the Russian army left the baltic states in the 90's they destroyed what they couldn't take with them, leaving the three fledgling countries completely defenseless.
A general observation: if Russia is so worried about security and genuinely wants a friendly neighborhood they might want to work on their routine.