I think SM20 could add a feature in contracts , where you can specify the Squad status in the contract for each player that you are signing.
Example : I buy Gotze but I want him as a substitute , so in the contract there will be a feature where you can define his status in the Team.
Squad status :
-Key Player / First Team
-Rotation / Backup / Hot prospect / Youngster
-Not needed
With this feature the bench players will be happy or at least not with red moral . And we , managers , can organize our Team better.