There really should be a system for faction destruction. For example if a kingdom has no fiefs left it should cease to exist, and wars with that faction should automatically end. The encyclopedia should update to reflect the new state of the world.
Tribute should also be capped at a certain number that is determined by number of fiefs owned for that faction so that when wars end between factions that have massive differences in power it doesn't end up turning the weaker faction into the Weimar Republic in terms of reparations.