I dont think we need a huge turnover if we go down. If we miraculously stay up we need a whole new squad, but if we go down I think we have players good enough for that level, considering the ease at which they won games against Norwich and lower league sides in the league cup.
Gk: Heaton (c), Steer, youth
Rb: Guilbert, ***new signing***
Cb: Mings (vc), Konsa, Hause, youth
Lb: Targett, ***new signing***
DCM: Douglas, Nakamba, youth
CAM: McGinn, ***new signing***, youth
RW/LW: El Ghazi, Trezeguet, Vassilev, Barry
CF: Wesley, Davis
Basically think we will need to replace Grealish, Elmo and Taylor. Preferably with young british players who will develop over the course of the championship season and be useful in the premier league the following season.
I dont see the point in signing new wingers or strikers because we will only need to replace them again once we get promoted. Forwards are the biggest step in quality between the championship and the premier league in my opinion.
Anyone not listed above can move on. Besides maybe Jota, who could potentially fit into the Grealish role at championship level.