Fun idea - New version of a Wizard where you choose between being an academic or pact wizard at first level.
Academics get a spellbook that they can add to freely, the ability to consult said book to swap out prepared spells, and some other benefits related to being a scholar of magic.
Pact wizards get a familiar who stores spells for them, as a gift from the being they made a pact with to learn magic. The familiar learns more free spells per level, but you can't add more spells to it because it's simply passing on information on behalf of another being. For the same reason, you can't change out spells once prepared. You're under contract, and the terms state when and how often you can request new spells. However, you have access to all of the assistance that a familiar spirit can provide, which includes help with concentration, and giving your spells a bit more "oomph", since you're not relying solely on your own power to cast.
At around level ten, maybe as late as thirteen, you get whichever option you didn't pick initially. No matter how you started, being a Wizard eventually leads to the same place. Either you start out with a purely academic approach to magic, and eventually forge a pact with a more powerful being in the pursuit of further knowledge, or you start out getting help from a higher power, and eventually learn enough to start understanding magic on your own terms.
