I read on CK2 wiki that ecumenical patriarch can also hold multiple pentarch titles at the same time if desired (http://www.ckiiwiki.com/Autocephaly#Pentarchs), and that this can be used to extend the ecumenical patriarch's authority over multiple de jure patriarchal regions. I have always wondered how I could make the ecumenical patriarch be the religious head of all my subjects as the Byzantine emperor, but granting the pentarchy titles to the ecumenical patriarch hadn't occurred to me.
Following this strategy do the pentarchy titles on succession pass to the next ecumenical patriarch or do they have separate elections (thus negating the benefits the moment the ecumenical patriarch dies)?