New realms can be created through secession, too. Also, it's way better to gain a solid peace with steep demands than more regions you can barely maintain control over. I'd like to see a tribute mechanics implemented 
You pay tribute by loading up a noble with lots of gold(not bonds) and sending him off to another realm's capital to send the gold. Of course he has to pay 50 gold fee, but you can rectify that by just giving him an additional 50 gold to compensate.
