Any new manager here faces the same problems the last three have.
If things are to truly change Moshiri needs to buy out the others and take full control, appoint his own CEO, DoF. They then can make permanent back room staff appointments of their own.
One hopes that if those appointments are good, there is a high-quality stable foundation to persist beyond first team coaches/managers.
I think there’s a good case for leaving SA where he is and changing only these other roles. Stability in one aspect and change in others. He certainly seems unlikely to get the team relegated. After things have settled, he may want To move on or may not want to move on. That will depend on what his new seniors ask of him.
Even if any new manager was great, how well will they truly do with the current senior setup?