After playing the piano, it should be encountered in the Nibel Reactor.
Ok, I didn't think it was like Zangan. Thank you for your answer, I can't wait to see it !
A battle rush isn't overly complicated, you just set the Next Battle flag in the formation so that they activate in a chain. Karifean's mod (http://forums.qhimm.com/index.php?topic=14937.0) does it this way, with the addition of a menu to select specific fights to start from + scales and adjusts the bosses to match an end-game party. I think that would be the right approach for it as it's not worthwhile to fight older bosses with an end-game party without adjustment; they'd go through the majority of them without any trouble.
I didn't know this mod, it's a good idea.
But I think the real challenge in the Satsuki's version is not really the difficulty, but the endurance it takes to make 700 fights in a row!
I have a message for those who say that the documentation is not update, or who say they don't find an item, a materia or an enemy skill : you should use Wall Market, Hojo and Proud Cloud softwares. You will find all informations about magic, enemy skill, states, enemy's weaknesses, enemy's attacks, what they drop, how they transform and what they have to steal. I made this and it's very very usefull !