An interesting way to bring Jon and Aegon in the story is combining the them with the Quentyn plot, but with a twist. After getting separated from Tyrion, they arrive to Mereen just as Dany gets married. While somewhat happy to meet a living relative, she politely refuses their proposal. The Sons still try to kill Dany, she flies away on Drogon and civil war erupts. The Griffs
successfully steal Rhaegal during the confusion and get the hell out of Dodge. In the meantime, Tyrion and Jorah follow their slavery arc more closely and give us eyes on the Yunkai army marching to Mereen.
Also, Michael Cera as Young Griff.