Thats why I use witch as a title.Personally, I would like to see a wizard subclass (for the classic curses-and-polymorphs type), a druid subclass (for the green witch type) and a warlock patron (for a more coven/dark take). Assuming we only get one, I think the wizard one has the strongest pedigree, but I'd take a warlock pact if they want to keep it confined to warlock.
Still, in an era where subclasses and feats allow for lite-multiclassing, the witch as a wizard/warlock hybrid isn't out of the realm of impossible.
Some of our witches are wizards, some are druids, and some are warlocks. You described exactly how we play it.