Originally Posted by
Duality
You're right about the final aeon becoming sin, but as seen by the statue of Lord Zaon's fayth in Zanarkand, once the FA core of sin is destroyed, the statue is no longer useable, so the pilgrimage aeons could not possibly be successful final aeons. There are however theories that temple aeons were final aeons to someone, but the summoner then chickened out / died en route after getting the FA / died fighting sin before they could summon the FA / or the summoner final aeon combo was so pathetic that it couldn't kill sin. This would leave a fully useable fayth statue in Yunalesca's closet of fayth, which someone could just take out one day and install in a temple, like Seymour and Anima.