this. make vassels more helpfull(i.e. them attaching armies to you) to compensate for lowe rlevies. vassels want a share or reward for new conquests they aided in. more tolls against large rebellions(if duke derp the first owning half your nation rebels and you win, you can confiscate pretty much all his titles if you beat him and some if he surrenders, which your vassles(or his if they sided with you) want an part of, or claims on their rivals territory who didnt support you but remaiuned neutral. wouldnt just make the system mor eintresting and all but also nerf blobbing as continued blobbing is going to make your vassels powerfull as well.