I'm all for this. If Homebrew Browser is able to install apps, then with a simple code to be able to rename files to more conveniently download hacks, this should be very possible. One issue I should point out is how people will be putting up files (in zip files, with images/other files, etc.) which could be solved with having people follow a certain format when uploading hacks (such as textures being uploaded uncompressed/unzipped beforehand, with only either or both of the paired .pacs or .brstms and no other extraneous files like a ReadMe or snapshots, while other more specific and complicated downloads such as .brres or only parts of of the .pacs and such, be uploaded to brawlvault but without access to them on the Wii. As for how the app will know where to place the files, we'd have preset location/redirectories for them. The user would be able to choose through a simple GUI that narrows down the preset locations until they get to the correct one (Choose Fighters, HUD displays character selection screen or similar, choose character e.g. Mario to choose corresponding folder, then choose from the 10 or 12 Portraits, the ideal ones being ones with numbers like the missing texture portraits from cBliss, which names it correspondingly e.g. portrait 02, file(s) get renamed as FitMario02.pac/pcs correspondingly). To improve upon this we might let the app use the common_5.pac files and such to use for the interface. The difficult part would be letting the app EDIT files, as it would need to be able to do what BrawlBox does.
there is the homebrew browser app. it has a way to un-RAR files and ZIPS so you could probably use coding from that. perhaps it would be better to start smaller and work up from there. like maybe a very basic downloading app that allows you can extract, move, and rename the files after you download them? i think other edits can be put off till later tho, such as editing the common.pac files, etc.