It would be more useful to be able to define the threshold of power for which a faction warrants a notification.
In my experience, most factions formed are nonviable - some envious landed brother forming a faction to support his own claim, with 12% of the liege's power, including his sole, lone supporter from his homosexual lover in Iceland.
I would, however, appreciate an option to get the notification when the faction power reaches 50%. It usually only triggers at 75% or 80%, at which point it is too close to too late.
Gameplay tip: don't focus too much on painting the whole map your color, regardless of internal organization. The time spent waiting for your threat to decrease is not best spent growing fat on lavish feasts - it is best spent on brutal, systematic civil wars to reorganize subrealms, one by one, along balanced and neat de-jure lines under same-culture dynasts, who are both awed by your many dynastic murals and books, and terrified by the implied threat of the execution of their children under the guardianship of your court geniuses.
