I would never want this unless I needed to give clear and obvious consent to enable it in the first place, and have access to a 'reset to default and never change again' button. Ideally I'd probably also have 'good change' and 'bad change' buttons to point it in the right direction.

This is so far removed from actual A/B testing that happens in the real world that it's unhelpful to even pretend it could be.