Yeah, some of us have been asking for this for a long time. Looks like CA listened
The side effect is if you spam protectorates, the campaign will become too peaceful and boring. But at least you can just cancel the agreement now, instead of having to declare war to break it off like before(another prayer answered btw). It's a little wierd but it works: you have to choose cancel alliance, which will turn the protectorate into an ally. No penalties whatsoever.
You can go further and cancel the alliance too. In this case there wil only be a penalty when you and your protectorate/ally share an enemy, in which case you'll be backing out on your friend.