What paths could a character take, alongside Templar?
Bardmancy: Up to 4 slot? That might be a bit of a loss. Though, I guess it wouldn't be too tragic.
Housemagery: One Slot, so it works anyways
Voidal magic: With the magic 3 slots in prevents voidal rituals (because you need 3 slots in voidal), such as a Arcane Scion, which is probably the only way a Templar would ever go. I could imagine interesting roleplay could come a Voidal Scion, as it makes one possible even more berserk. However, Scions have a tained soul anyways... should that even be possible? So I really think nothing of value is lost. Any other voidal magic would be immensly strange to take up anyways, as it weakens the body...
Voidal mages truly become useful with a feat - which would probably the Scion here, anything else would make no sense. However, due to the tainted soul it would incompatible anyways? Or would it be, due to Malchediael having been tainted himself?
Im no expert on that one.