Why are you worrying about this now, when the likelihood of it happening in the next month is next to nil?Again, Berry can still play midfield minutes if he's starting in Murphy's role. This would just be to solidify his position in the side by having a role that he can make his own while he is cementing himself as best 22.
Sure, they can plan for the future, but there's no need to worry about it now. Crouch is a month away, Hately's a break glass in case of emergency player, and Pedlar is about to play his first SANFL game. Berry's position is completely secure for now, and there's no need to worry about re-roling him for the foreseeable future.
** And Murphy's position is nowhere near as insecure as you think it is. Berry will be dropped before Murphy, and you can take that to the bank.