My stance is that if you want to get rid of the bad eggs then there can be no sacred lambs.I don't think you necessarily need to exit the entire problem group. I do think you need to exit enough of them, alongside bringing in Poch, and new players with better mentality, to change the culture. Mickey for me has enough abilities that I wouldn't rush to exit him under a new coach, though I take your point.
Micky is also a far more prominent voice in said leadership group than Porro or Bentancur for example. It may sound rough but Micky, Romero and Vic are the guys that you cull to make an example for the rest. Just like Poch did when he took over.
Micky is obviously a very good player but if he's set on leaving and is a proper locker room negative then he needs to sold imo unless the new manager manages to completely win him over.