Hopefully there would also be some consideration towards creating a balance of power through alliances. After all, if there are only one or two main powers in the game, then the weaker factions should want to have some safeguards against aggression from those factions, either by allying with one of them to force their involvement in case of war, or by forming a coalition of minor states which would at least be problematic for the dominant factions to absorb.
Also worth considering would be alliances for mutual growth at the expense of a common neighbor, or mutual defense against a common enemy, or securing a border while distracted by other wars (non-aggression pacts would do for this, unless there is a neighbor who won't take it, but if you can pick up an alliance or two with neighbors of that faction it should be less likely for that faction to go after you while you fight your other wars).
Powerful factions with expansionist tendencies should be more inclined to conquer their neighbors than form alliances with them, especially if the power difference is large, but the existence of such a faction should also encourage the weaker factions to form alliances at lower cost, either with one another or with the major power(s).
