Quote Originally Posted by Didz
On a secondary point: Can anyone confirm what impact vassalage has on Faction Goals and diplomacy, for example, if Scotland were to make England a vassal state would that satisfy their faction goal for the Short Campaign or does elimination mean exactly that,
It won't satisfy the victory conditions, you have to eliminate the faction. But vassal's provinces are considered to be under your control, so you don't have to actually conquer 15 provinces (or 45 in the long campaign) to met the victory conditions. Except of course, if your vassal is the faction you have to destroy to achieve the victory.
Quote Originally Posted by Didz
also is is possible to declare war on a vassal without going to war with its protector?
I think it is, but I'm not 100% sure. As someone already mentioned, the vassal can have it's own allies and enemies, independent of it's master.