i don't know what "empty war" should mean?
It is usually referred to as a situation where a war is declared without any intention to ever fight it, in order to garner some benefit from game mechanics.
Say, for example, that having a diplomacy status of War with a realm would cause your realms to generate 10% more taxes. In this case, you could be sure that realms would make sure that they declared war with at least one other realm, for their mutual benefit, without ever intending to fight that war. i.e. Sirion and Eponllyn declaring war, or Strombran and Minas Leon, or Niselur and Grand Duchy of Fissoa, etc.
These are the kinds of things that we have to watch out for when considering new game mechanics. It results in everyone avoiding the proposed penalty, or gaining the proposed bonus, by acting in a way that makes no IC sense. Essentially, all you do is implement a penalty that no one suffers, or a bonus that everyone gets, and make the game make a little less sense.
would someone count how many battles are waged within a week to declare some war is "empty" or not?
currently i am involved in at least two realms in war where there were no a single battle in a month time for different in-game reasons.
That's really the whole point. Game mechanics couldn't really tell whether it was a "real" war or not, without making the wrong decision from time to time. That's why these types of mechanics, that rely on nothing more than a player-declared state, are not good mechanics. They are easily gamed.
instead of giving weight to player-tailored diplomacy, we have situation where majority of diplomacy influence is related to random-generated peasants mood toward realms. diplomats should spend majority of their time to fight brainless ai-machinery.
I tend to agree. We do too much peasant management in the game. One of the things the dev team is discussing is ways to remove the peasant-oriented focus.
the same things is with building shutting down in regions for no any traceable reason.
That is implemented to introduce a bit of randomness into the game. With the recent bug fixes to buildings stockpiling paraphernalia, it shouldn't have as much of an effect as it used to. Perhaps with the exception of the smithy. But then again, you can always build a second smithy to reduce the down time.
and on top of it there is "wounds worsening"
Along the same lines, it introduces some randomness. It also makes it more painful to play older characters, and provide incentive to retire them and start new, younger ones. This helps break up the power structures, and let some new characters take their place.