The Warrior of Light has already canonically engaged in a form of 'necromancy'. A couple of relic quest stages involve absorbing the souls/aether of sentient beings in order to empower the relic weapon which is then, potentially, used to cut down the loved ones and comrades of those very same sentient beings. There's quite a number of examples of the Warrior of Light and their allies doing things that they claim are 'unforgivable' when somebody else does it, so I don't think it'd be too much of a stretch to introduce a job that leans on darker, more dubious magic.