Builder line gives + General Loyalty and + population Happiness
Steward line gives Happiness and +% agric. production. Which is awesome. Even if you have a bunch of provinces not worth building up agriculturally, if you have mon-ay and a young Monarch, go wild on them, get your Monarch to the Magnificent one and hey presto, + 1/5th agricultural production. I'm well aware of these traits.

Roark:

I *can* go to war and I have no problems going to war but I was wondering if there's any way to go about it *without* going to war.

Now it seems there isn't, lal.

Is it cheesy to remove the bad apples from your royal line? Maybe. But if you are an actual King you get to CHOOSE who your heir is.

They should've implemented that in MTW from the get-go. Makes much more sense. Plenty of actual Monarchs have done so, altering their heir.