So I downloaded BY's Riivolution "hybrid" that allows you to use the Gecko layout for your SD Card (X:private/wii/app/rsbe/pf/fighter/zelda) so that Riivolution is easier to use. I noticed in the Readme that you shouldn't use the file Patch code.
So I had a theory. Note that it's only a theory, and I have no idea how Riivolution is programmed.
It appears to me as if Riivolution has it's own file patch code that allows for Sound Effects editing, that apparently the file Patch code used by Gecko (which was made by PhantomWings) does not. So, what if PhantomWings updated the file patch code, or made a new code to allow Sound Effect replacement on Gecko? That would technicaloly render Riivolution obsolete, because Gecko would be able to do just about everything that Riivolution does, plus snapshots and replays.
It's a thought. SFX editing is a relatively new process, so PhantomWings may or may not be working on a code already.
Riivolution will not be obsolete. See, what Riivolution does is making the game load files from SD card instead of the disc (AND apply codes). This does not work only with Brawl, but with other Wii games too.
Best solution? Use Riivolution. Or swap the files in ISO (like you may have already been doing before).