I could see GEO working as a ritual-based job, maybe using spell combos like NIN do with their mudras, or stances like BLM's but with a dynamic unlinked to mana, to trigger unique spell effects, and also focusing on their aspect of banishing wicked spirits. I don't think their current similarity to both AST and CNJ is a huge hindrance to their addition, as SE could easily embellish on their ability set later on. SE had an Onmyoji styled caster dps in the concept stage for SB, which was cut in favour of RDM, so it's not like they would be working from a total blank slate, unless the concept was really bad.