A few weeks ago, I posted my redesign of the bard. https://input-command.tumblr.com/post/624037531349024768/input-command-the-bard-their-magic-comes-in
This one is a rethinking of a typical mage or wizard. What if the fuel for magic was the wand itself? A wand with low density might burn itself out in one shot, but one with more density could be used multiple times. And larger wands could cast larger spells. If you could wield an entire tree...
What this naturally leads to is Botany: The study of plants and how to grow them for specific desired effects.