For instance, renaming the sorcerer class is one thing. However, a big thing in this world is the originate ones -- ones who, owing to some influence around the circumstances of their conception, have spells that no one else has. These spells are concentrated around their origin, and unlike a D&D or Pathfinder sorcerer, the spells can be divine/clerical, arcane/wizard, primal/druidic, etc. Such sorcerers are immensely valued because their spells can be back-engineered. The church regards them as divine gifts, the fount of spellcraft. (Spells can be devised, but on a basis provided by the reverse engineering.) Later sorcerers, their offspring, can also sometimes originate spells.
In a D&D world, unless this is very much the backstory, it means seriously restricting the spell list. All spells would have be divvied up in advance for which sorcerer introduced which type, and no other spell-caster could use something from a future list. The original, primordial sorcerer would have to be in a world with no other spell-casters. (Or sorcerers. I think there will be a wizard sorcerer, a druid one, a cleric one that introduced the basic types.)
True, associating with such a sorcerer would give a wizard a shot at unique spells. . . .
Also, of course, the higher level the sorcerer, the more spells. At first sorcerers were forced to adventure because their magic would run wild if not used, and the rulers hoped to kill them off that way. People who wanted to reverse engineer their spells had to do it on the sly. And carefully protect them in battle in hopes of keeping them alive. (It wound down. At the latest point in history I've worked on, you do have to be trained, but either they send you out to kill a few goblins, or they have you swear to defend the kingdom and figure that being ready to act is good enough -- though many a sorcerer decided the route to wealth was lots of adventures, lots of experience, and unique spells to sell.) But a party where one character had to be coddled and prioritized by the others is an -- interesting dynamic.
And once reverse engineered, well, there's the church, and various guilds, and other organizations, and even lone wizards, but as a rule, the larger the organization, the more spells you can learn, and the more duties you must do. That restricts it, too, though the players can choose the trade-off.