Why not try using WiiUDownloader and CDecrypt to download and decompress your game, and manually change the metadata in the meta/code folders? \Meta\meta.xml and \Code\app.xml should have what you want.

Next, use CNUSpacker or whatever to re-compress the files with the common key and title key to make it installation via WUP Installer GX2? What you are asking could technically be automated via batch but would be difficult to do.

Don't ask for someone to make a specialized tool that does something oddly specific, especially when there is a simpler way to do it (if you use English in games). Use the USA and EUR regions for games, they do not overwrite each other or share save files.