Is succession valid if the Imam only needs to give the concluding salutation (Taslim) when purity breaks?

Primary text

Succession is not valid when the only remaining action is the concluding salutation. If the followers complete their prayer before the Imam appoints a successor, they do not need a successor because only the Taslim remains. My considered view is that succession is not valid in this case because if the successor builds upon the prayer, he sits in a place where the followers should not be seated (as a follower leading), or if he starts anew, the followers sit in an incorrect position relative to him. Succession was only established by consensus where neither of these positional anomalies occurred.