if your going to swap sound effects, id imagine you'd have to open up where the sound effects are stored, and edit it there. (i forget where exactly lol it's been awhile since i've dabbled at this.) WallMarket from what ive seen lets you Edit the appearance/textures by swapping model id's, as well as animations (i've made Shield look like FullCure, etc.) but not their sound effects, unless you switch the animation. IE: Shield does not sound like Shield, when FullCure is the animation being used for it. the same applies to Ultima Weapon and the Masamune. if you give the Ultima Weapon the Masamunes Model/Texture ID, then it'll make the sound the Masamune does, while looking like a Masamune (30ish% Sure, ive edited the Masamune to be equippable by people other than Sephiroth and it had.... weird effects, they carried one of their original weapons like when Cloud had it on it was a Buster Sword, Aerith had a Guard Stick, and Barret had his Assault Gun Lol.) but yeah.. just experiment for the most part and see what you can come up with.