My take on politics and war in DW is that it is much more of a grey area than what you see in most other strategy games. You can already attack and even destroy assets belonging to other empires without declaring war, and there is absolutely nothing that says you have to attack when you do declare war. I understand it to be more of a political statement about who is on what side of an issue rather than an overtly aggressive move with the intention of invasion and conquering. With a large number of races in the game I see huge mutual defense pact groups form, but with a few members who hate each other and eventually declare war, thus forcing everyone in the MDP to pick a side among friends. Eventually I expect this repeated side picking to settle down into established allies and enemies that might be different than what you would expect based on racial biases alone, and eventually it should lead to more prolonged violence and larger scale war.
Consider real life. Many countries are constantly on the verge of war and go through periods where they fight and where they declare cease fires, often with very little loss on either side. This is mirrored in many ancient tribal societies that were constantly "at war" but rarely killed each other. DW does, in my opinion, a decent job of managing realistic interactions regarding war.. you just have to change your expectations away from the deterministic politics that most games use.
A little out of left field for this conversation, it might be helpful if the game was able to determine key assets belonging to each race.. I find that my mining facilities in other race's territories are worth a huge sum if I trade them away, but they are typically nearly worthless to me in a practical sense. However I undoubtedly do have a few facilities that mine rare resources that are critical to my empire, and it would make sense for feuds to erupt over rights to such scarce resource planets.