Fletcher, McKenna, Phelan, I cant see any of them leaving unless they asked for it like Carrick. These people have been at the club for a long time, replacing them will raise eyebrows of other people who also have been at the club for a very long time, including some of the ex players and pundits.
Ralf cant afford to do that. And its not neccesarily because theyre british - Moyes brought in his own staffs and got criticized for it eventhough he was handpicked by Sir Alex. Both van Gaal and Jose as crazy as they were, knew there had to be United people around him, they had Giggs and Carrick.
Its not about nationality. It has something to do with change. And its a change after how many years now..? 20 years+. It will always be hard to take. It needs to happen gradually and Im sure Ralf is smart enough to recognize it. Change every familiar faces in an instant and he puts himself at risk to be criticized for every single mistake he does, much more harshly than if he didnt. And the argument for those can easily be justified by a simple "he tried to change United".