Hello. I may point out to this comment of mine. This PC of mine was optimized to the best of my abilities to be a generalist mage, spontaneous-only specialist, Mystagogue, Seeker, and would-be immortal with Unstructured Caster and Rigid Magic. So, I daresay it is a treasuretrove of ideas on how to manage this kind of character concept. Feel free to take inspiration from this as you deem best.