So if there was a practiced mage who was sent back, due to the knowledge-based nature of magic as described, they would basically still have their failed timeline magic ability completely intact? As compared to an Aura which would likely need at least some training since it's more of a muscle than pure technique?

I'm not necessarily calling it out as an imbalance and maybe you answered that question already but I just wanna be sure. I think having a magic system would be fine, though I might have a slight preference to just a wider array of Aura options over Aura and Magic coexisting.