I see your point but in my experience, this would end up into being a monster method which holds far too much logic in one place. I think this boils down to a personal preference to be honest, everyone has a different mindset when developing but I usually prefer to have many small and testable functions more than just one gigantic one.
Either way I agree it would be super nice to have some extra goodies from controller to be able to manipulate/organise data in different ways. I really like your idea of a transform method that could be used to standardise output! 