Any% NG+ is already a meme category.
https://www.speedrun.com/nsmbwmemes#Any_NG%2B
The difference compare to "Any% without cutscenes just for getting a WR lol" requested by Exciton is in NG+ you just play the 8-Castle.
I'm not a mod but I think NG+ will not be added on the main board except if the category take popularity.
First off, if this were ever added it would be a meme category. Second off, it has already been decided. No it will not be added.
My solution would be to make a NG+ No World Select where you can't use the minus button to jump worlds, you must start in 1-1, and all items that you have going in are allowed. Cannons are allowed, but no other method of world jumping. I was actually wanting this to be a category so this format would make sense, maybe as a sub-category for Any% NG+ or a new Category Extensions (Meme category) all together.