Whenever I think about this game, I think of Super Mario Bros. Deluxe, the 1999 GBC port of the 1985 NES game. That was arguably the most "deluxe" of any Mario series port ever. I mean, it had the original game (plus saving and world maps), a new Challenge Mode with Red Coins and Yoshi Eggs, a multiplayer VS mode (and its single-player variant You VS Boo), and the Lost Levels in tbe form of Super Mario Bros. for Super Players. It was definitely the definitive version of Super Mario Bros.
With that in mind, I wonder just how "deluxe" this version of NSMBU will be. When I look at the different modes of SMBDX, I see that NSMBU already has a lot of them.
-The standard mode doesn't really need to be changed. It already has a couple new characters; let's leave it at that.
-Challenge Mode is essentially present in NSMBU; it literally has a mode called "Challenges", as well as Boost Rush mode and Star Coins. Other than new Challenges and Boost Rush packs, there isn't much to be added here.
-There is already a multiplayer VS mode in the form of Coin Battle (or maybe Story Mode, if someone decides to start a death fest). Again, not much to be added here. But some free-for-all minigames are always welcome!
-New Super Luigi U is this game's equivalent of For Super Players mode. It's essentially a more challenging NSMBU with a whole set of 82 new levels. I wouldn't say any changes are necessary here, but they already showed Mario being playable here, so that counts for something.
In short, I can't think of much they can add if they take the SMBDX route. But hopefully, they'll surprise me and add stuff I haven't even thought about. Hopefully, this port will be worthy of the "Deluxe" title; after SMBDX, NSMBUDX has a lot to live up to.