The real Warring Triad trial
I was thinking that it would be kind of awesome to have a trial featuring the 3 members of the Warring Triad, Sephirot, Sophia and Zurvan in one single fight. This would require both tank to take Sophia and Zurvan while all the team has to pay attention to the gigantic Sephirot's attacks. It would be kinda cool and would allow the possibility to add a Warring Triad bird which would play "Battle to the death" and then put "Fiend" back on Sephirot's bird while renaming it Sephirotic lanner.
The intro to the battle could just be something like EX training but if all 3 were to be released at once and the battle could take place on an Azys Lla island.