I don't like the mechanism with alliances.

[Martok]

The AI traditionally makes its diplomatic calculations based on the probability of if it can win a war in a specific province, thats the trend in the Total war series and given the time period of empires that absolutely has to change.

Agreed. One of the strategic AI's main weakness is its shortsightedness. It's unable to see the larger picture when considering whether to attack someone -- all it can see is that a border province belonging to Faction A is under-defended, but fails to realize that Faction A has large armies in the provinces next to it. The AI needs to consider a faction's overall military and economic strength when determining whether to go to war with that faction, not just the local situation.