While it would be cool and definitely make it the best path. I think for balance sake, it won't happen. At least until much later in the game. And I think that's why Mage Elis got nerfed and relegated to being Elin portal buddy. Because he would be too powerful for most of the encounters if he had his magic still.
For example, his compulsion/suggestive magic he used on Rosa would be pretty potent against other characters if his magic got better. And since no one else seems to have that magic, outside of Sera's being like an advanced version based around illusions. He would easily manipulate certain characters. Since magical resistance doesn't seem to be a common thing in this world.