I love the suggestion and it's great to know that it's on development
But I think that bloodbending should as another variable, instead of just the Bloodbending that works at any time
I believe that there should be two different variations:
FulltimeBloodbending: 15 (like Amon, Tarlok and their father)
FullmoonBloodbending: 30-40 (like Hama and Katara)
In the show FullMoonBloodbending is an easier ability that can be learned quite easely by skillful waterbender (Katara did it pretty much instintively, just by seing Kama doing it...
) and used only during fullmoon.
Since that is only like once each 30 nights, I think the night buff should be enouth to let waterbenders use Bloodbending, otherwise it would became kind of an useless ability...
If you desagree then there should be at least the FullmoonBloobending chance to bloodbend during the fullmoon.