Sooner or later, your reporters will object to converting conversational sentences into heavier prose. Now, you re ready for stage two. You suggest that they draft their sentences in the active voice in the first place. Composing in the active voice takes half as long as conversion. One more step toward real sophistication.
Writers find active sentences easier to write if they seek out the actors during reporting.
Teach your interviewers to notice when their subjects hide the actor by speaking passive sentences. So you can edit in the active voice by teaching them to report in the active voice.