Something I'm actually keen on doing is spliting the Demonmancy school into two disciplines and having herbamancy and vitamancy cannibalize Noxomancy. If you moved necromancy into the Lues School and Obligatio was purely two opposite things within what now fall under demonmancy would be best. Split it up into the people that are eventually going to fall and become demons and the people who are basically demon hunters and use aspects of the Inferno that are not directly related to summoning demons. At the beginning they would start out the same obviously but which school you were doing would become obvious after you pass into the Adept rank. This way you could just balance the two against each other and have sufficiently rearranged enough power from the main tree to keep the other mage blood competitive.

Note: Lucius has been talking about something similar for awhile atleast in regards to demonmancy.