It's not simple like that. Key players want to start big games. You may be able to convince and keep Ben Davies happy with those low profile league games. I don't think that's the case with Bremer, who can start for all the Italian CL teams, and he's being heavily linked to Inter, too.
A CB in back 3 is the position that doesn't see as much rotation unless it involves injury and (under)performance issue. Italian teams have had some old CBs with long life shelf as starter. Conte management style is based on Italian principle of course. Gametime is not equally divided, especially the CBs often still play a majority amount of matches in a season, because in theory before you win a game you're required to "not to lose first", which a settled backline is the keystone of the gameplan. It's easier to rotation attacking players than shuffling the defense and expect a consistent standard.
If Bremer is signed, I don't see us commit big money for another CB just for rotation. It maybe another punt cheap signing.