Unpack battle.lgp. I'm not aware of the flaws of LGPtools - should work just fine, but lgp/unlgp is an easy commandline tool and it's said to be better, and works even faster I would say, so use it if the word "commandline" isn't a black magic for you=].
Take your Masamune model by default it's "sack" Sephiroth: Masamune, rename it to "rtcu" for Cloud: Nail Bat or "rtck" for Cloud: Buster Sword(not sure which finally you wanna change but you can find all known info about battle.lgp on wiki - I usually turn nailbat to masamune and turn it's power to rise with enemy lvl or killed enemies, yet I don't really use seph patch), you can also change all models with masamune if they look bad coping the masamune model a few times and renaming it to all Cloud weapons from rtck to rtcz(or look below for other method). Pack your battle.lgp again.
You can edit weapon stats, sounds used easily without any hex editing(at least for most usefull stuff) now by Wallmarket - you can also use it to change model of all weapons to look like other one, but it must be one of current character weapons anyway or so I guess in case you wanna use sephiroth models.
And for the music there was Aali's patch, I'm lazy to look for original topic but you can find it here too: ff7_lessdebug -
http://forums.qhimm.com/index.php?topic=6238.0 never fooled around music yet soo I dunno really if it'll help you, but it does cut off debug info unlaging/speeding up music.
