For my submission, I’m working on a class for Basic Fantasy RPG (though by nature it’ll be cross compatible with a bunch of old/retro systems). My approach is to base it on the magic user class (for xp progression, saving throws, etc). I’m going to modifier the spell list (combo of magic user and Druid), though instead of spells in the traditional sense, I’m reflavoring them as tinctures, salves, and charms. They will take longer to prepare, but can be used by others as well. They will have a familiar, which will be the spirit (in animal form) that they draw their power from. The familiar will provide added utility, but if it is killed it will harm the witch, and weaken their power until resummoned.
Anyway, that’s what I have so far.