The arcanist has an archetype that trades out their spellbook and wizard spell list access for a familiar and the witch list.
It doesn't have hexes, which kind of sucks, but the fact that it can be stacked with other archetypes (including wizard school access or sorcerer bloodline access, or the brown-fur transmuter), makes it an interesting choice.
EDIT: One way of looking at it is that the Unlettered Arcanist isn't an arcanist with a different spell list, but actually a witch with different class features.
Well, since the Paizo team saw no problem giving the arcanist access to the witch list using the arcanist casting mechanic, I see absolutely no reason not to create a witch archetype that replaces prepared casting with hybrid casting. Especially since the arcanist has the same number of spells per day.
However, since the witch's class abilities don't typically have much of a use limit, as opposed to the arcanist which has a limited reservoir for their class abilitiers, I would recommend that the patron spells, though added to the familiar for no gold or time cost, still have to take up prepared known slots for the day like any other spell. If there's a spell the witch really wants to have permanent access to, they can take Preferred Spell, which also lets them add metamagic to the spell on the fly without increasing casting time, which is superior to an arcanist who has to use a higher-level memorization slot and has to pick the metamagic feats ahead of time and has to spend an exploits known slot and spend a reservoir point to add any extra ones on the fly.
EDIT:
Interestingly enough, the first "cast spontaneously, but change your list each day" class for the d20 system was the 3.5 spirit shaman, who had a spirit animal that would go out and bargain with strange powers each morning to "retrieve" the spells the spirit shaman would have access to that day. Thematically, that is very similar to the witch.