Visiting visa -> Leaving China -> transit type

Hey, I just wanted to make sure that I'm understanding everything right. Following situation:

I'm first planning to visit a friend in PRC (I have a visiting type for that), so I I'd like to book a round trip to Shanghai. After visiting him I want to go to Japan for one week (visiting type will have expired at that point), then go back to Shanghai and take my return flight. For that part I would like the transit type.

Since I'm actually leaving in between and going Japan -> Shanghai -> US for the return trip there should be no problem whatsoever, right? I'm not 100% sure how the airlines will handle my flight though. For the flight Japan -> Shanghai I will have no valid entry permit on arrival (Will they still handle the transit type if I'm switching airlines?), while for the US -> PRC -> US leg my entry permit will expire in the middle of my "stay" in PRC. Could any of that be a problem? I guess I could technically always just stay at the airport, even without the transit type.

Thank you very much for your great support in all things China!