I wanna hear your ideas of what a cool fight could be. I encourage you to all post something serious, and something funny/over-the-top.
For my serious idea, I think it'd be pretty awesome to fight a boss that splits your party into four parties of two, and forces you to work in teams of two to take down an add. And then later this mechanic is repeated but now you're solo :0. The add can and should be very tough; imagine fighting doing your level 50 job quest in sub 50 gear, and triple that difficulty. Failure on your part would buff the boss by keeping the adds alive and healers would have to go out of their way to raise you, or they would be unable to raise you at all, because maybe you can't make your way back to the arena.
For something silly, I do think it'd be fun to fight a gigantic boss in parts, like Titan in FFXIII...if we could actually fight him lol. Start at his toes and work our way up.
My first idea is for something like Coil level raiding by the way, and the second for 24 man casual/easy content.