Sephiroth sort has a perfect level of setups to be used in multiple Raids, here was the idea in my head:
Sephiroth travels through dimensions connecting the lifestream of FFVII to the lifestream of FFXIV to seek a certain power to bring back to his world.
Sephiroth creates a memory construct of the Nibelheim Mansion as the central hub for players in the FFXIV lifestream, but unlike previous hubs this is a public hub for players outside of parties to gather (I kind want of it to be a future social hangout too for players who like to be gothy, etc hehe) also maybe throw in that piano as a minigame?
Raid 1 - Nibelheim/Crisis Core Sephiroth (Music: Vengeance on the World)
This is just Sephiroth in his normal state, and fights much like how he does in Crisis Core.
Raid 2 - Bizzaro Sephiroth (Music: Birth of a God Soken Arrangement)
Three platforms with the party being split between them all; all have different mechanics to be dealt with. The goal is to break down his parts and destroy his central core. It will be something FFXIV has not done yet partially.
Raid 3 - Seraph/Safer Sephiroth (Music: One Winged Angel Soken Arrangement)
Pretty much how he fights in the original game, and maybe some new mechanics not throught of for his form?
Raid 4 - Advent Sephiroth (Music: One Winged Angel Advent Version)
This Sephiroth has never been fought before in any video game, and we witnessed his abilities in Advent Children, it would be cool to see can be done with this one. Maybe make his Geostigma like a countdown timer that has to be resolved before it destroys a party member.
Raid 4 Part 2 - Remake/Rebirth Sephiroth Savage Only (Music: One Winged Angel REBIRTH):
This Sephiroth combines all of his past abilities across time and space to really put the beating down on you and brings in Kadaj, Loz, and Yazoo as backup support (or maybe alternatively Jenova). He casts Meteor at the very beginning of the battle that is the Hard Enrage with a timer which causes the players having to beat Sephiroth before the Meteor falls.
Orchestrations to earn (for things that would be logical to hear and get):
Vengeance on the World (Crisis Core Theme)
Birth of a God (Original Theme & Arrangement by Soken)
One Winged Angel (Original PS1 Theme & Arrangement by Soken)
One Winged Angel (Advent Version)
One Winged Angel (Remake Theme)
Heart of Anxiety (Original Theme - Earned during the story)
Trail of Blood (Original Theme - Earned during the story)
On that day, Five Years Ago (Original Theme - Earned during the story)
Those Chosen by the Planet (Original Theme - Earned during the story)
Gear (based on Sephiroth's outfit):
I think it would be neat to see how Sephy's outfit would look if it was more based on different jobs in my opinion.
Outfit Parts:
Sephiroth's Coat
Sephiroth's Pants
Sephiroth's Boots
Sephiroth's Gloves
Masamune (Glamour Weapon)
One Winged Angel (One Black wing on your back) accessory
Hope you like my idea, it was in my mind tonight. :3
(Feel free to give your idea how it could work by the way)