While I do like the way war works in CK2 and I believe it does represent the way war worked at the time well-ish. I also believe there is a space for improvement. First of all, there have been actual peace treaties defining borders, cash payment, tribunary status replacing a ruler, etc.
Second of all, there has been a lot of tug of war like places within CK timeline, the Byzantine Empire with most of their neighbours comes to mind but also stuff like England vs France, England vs Scotland, Reconquista etc. A lot of those places would not have defined borders, so unless you sign an actual peace deal deciding borders you might be free to engage in small scale warfare - a raid here and there, a border province being captured, a vassal switching sides perhaps etc.
It also would not be bad to be finally allowed to do stuff like "I am going to overthrow the king of Poland and also get a massive cash payment from the new king, oh and also I am going to give me nephew this Polish county he has a claim on." All in one deal, of course, we could finally get deals that are not one-sided, most wars in this period, especially in Europe would end in some sort of white peace afterall ( well major ones that is. ). So after signing the already mentioned peace deal with Poland you also give them a border province they have a claim on, etc.
Second of all, there has been a lot of tug of war like places within CK timeline, the Byzantine Empire with most of their neighbours comes to mind but also stuff like England vs France, England vs Scotland, Reconquista etc. A lot of those places would not have defined borders, so unless you sign an actual peace deal deciding borders you might be free to engage in small scale warfare - a raid here and there, a border province being captured, a vassal switching sides perhaps etc.
It also would not be bad to be finally allowed to do stuff like "I am going to overthrow the king of Poland and also get a massive cash payment from the new king, oh and also I am going to give me nephew this Polish county he has a claim on." All in one deal, of course, we could finally get deals that are not one-sided, most wars in this period, especially in Europe would end in some sort of white peace afterall ( well major ones that is. ). So after signing the already mentioned peace deal with Poland you also give them a border province they have a claim on, etc.