Edit: I've just realised there is a much much older thread discussing this too. Here is the link to it: https://forums.thesims.com/en_US/discussion/680765/witches-in-sims-4/p1 With all those ideas f...
They should be able to have unlockable skills, like vampires. And they should be able to choose if they perform magic with a wand or by hand. (more powerful witches could unlock "magic by hand"