IV) And yeah, I have thought about precisely the same thing about what cats actually hunt in the wild -- small mammals, insects, grubs, etc.
It is quite difficult to mimic that diet unless you have a mouse-infestation....and around here, the rats are bigger than our cat (she's only 3 Kg - the litter runt). Also, cats are a big problem for the native wildlife populations here in Australia, so we try to keep her satisfied by providing her with enough food. She will still hunt the occasional mouse, but I'll just have to live with that. She's an animal, and she needs to practice/show off her offerings to her owners.
Which is partially why I want to make the change; if she can have a diet that closely resembles her natural diet, it would be preferable as it may deter her from hunting more for whatever she is lacking in her current diet (if that is what is happening) -- and she will be a healthier cat.