Higgins would probably try to sophisticate Steve. make him into a proper young man or something. Oh and I'm sure Steve would try to sneak around the house only to be cornered by Zeus and Apollo.

also, in between the time that his mother died and he was sent to Maine, Steve spent even more time with Magnum at the guest house

I can see a present day Magnum 100% on Steve's side and livid at Joe for the shit he's pulled recently. Joe may have shaped him in Coronado or whatever, but Magnum was probably someone he could always count on.