#2 John Cena could become a special commentator

John Cena would be a fine addition to WWE's commentary team due to his incredible mic skills. He would be a perfect replacement for Michael Cole on SmackDown or he could take Samoa Joe's place on RAW after the latter makes his return to in-ring action.
He could even become a commentator for big events such as pay-per-views and special shows. Whichever program he provides commentary for will see a significant increase in ratings each week.
#1 John Cena manages another WWE Superstar

John Cena would be an excellent manager in WWE. He is one of the best promos in the history of the business. He could make his promo skills useful by speaking on behalf of a WWE Superstar who lacks mic skills but is phenomenal in the ring.
Imagine if John Cena managed Aleister Black or former WWE star Andrade. Their careers would've reached new heights and they could've gotten the rub they desperately need to have a successful career in WWE.