I only support it if you can also manage rebelions better, two points.
1. You can negotiate with rebels, no you either accept or dont. When rebels have certain strenght they should be like a nation you negotiate with. Maybe taking harsch penatlies to ducats, monarch points and local autonomy, maybe even going as far as agreeing to release them as a vassal. Anything else then, oh shit rebels won, my entire country will just unraffle.
2. Allies can be called in to help after a certain point is reached, rebels also get acces to call in nations that support their side. Any rebellion going on for several months will draw international attention, many great wars started because of rebels. If the rebels dont get any support for their cause, allies will just crush it for their ally.
I would just like it if its a bit more dynamic then can you handle their stack, no problem, cant you handle it, exit campaign.