What is the ruling on the prayer led by an Imam whose ablution was invalidated during the prayer, so he put forward someone else who arrived late to complete the prayer?

The latecomer whom the Imam has appointed as his successor must observe the sequence of the first Imam's prayer, sitting and standing at the appropriate places. When the first Imam's prayer is completed, he stands to make up for what he missed. The congregants have the choice between concluding their prayer individually or waiting for the appointed latecomer, sitting until they can conclude their prayer with him.

The Malikis stipulate for the validity of the succession that the congregant must have performed at least one bowing (ruku') with the Imam who appointed him. They also stipulate for the validity of the congregants' prayer that they must wait for the appointed Imam until they conclude their prayer with him.