He's a paladin. He's got to he trained in holy/war, it's the only training that makes sense thematically. I really don't see a problem with him being trained in two major schools. If a mage is designed stronger in one way it will be weaker in another. Training isn't the end all be all of balance. We've already seen that the straywood beastmaster is perfectly capable of holding his own against the wizard of Sortilege, and the wizard is fully trained in two schools while the beastmaster is only trained in one. Meanwhile, the Druid is trained in two schools but only has level 1 training in the second school. In other words, a mage with more training isn't always better, perhaps because there are other aspects of their ability cards that balance out their training?
Also, let's not forget that the Sorcerer is going to be arcane/dark, according to one of the recent let's level up podcasts.
I would also like to point out that if mages could not be trained in more than one major school, the number of possible mages would become quite limited. If every mage could only be trained in one major school and sometimes one minor school, and if for each training there were two mages, one original and one alternate, then there would basically be a maximum limit of 48 mages [6 major schools * 4 minor schools * (1 original mage + 1 alternate)]. Unless you started having different mages that aren't alternates of each other with the same or extremely similar training.
