Super World X 1.1
Note: You cannot use old saves with this update. If you wish to play with this update, you will have to start from the beginning of the game. This is unavoidable due to how SMBX save files process changes to the overworld.
Whew! After much grueling testing today (several hours!), I've got SMWX done! I'm labelling this download as 1.0 in case there's anything that needs changing later.
Since there are a bunch of alterations to the core graphics/music/sound files, I had to distribute this as a full SMBX package rather than a simple worlds folder. To those who don't use SMBX, that may sound like gibberish. In order to play, all you need to do is download, extract, and run smb.exe!