This tutorial is for 4.1-4.5, but it will likely work very similarly with the upcoming Gateway update.
Create an emuNAND on your SD card, back it up with emuNAND tool, boot Gateway mode, go to System Settings, make sure it says "GW3D" instead of "Ver." before the version number, update the emuNAND to 9.4, go back to System Settings, go to the format option below the system update option (this will erase all emuNAND and SD card data but will leave the emuNAND partition intact), make another backup with emuNAND tool, and create or link a NNID in the NNID settings in the System Settings.
To have multiple NNIDs and prevent problems with bans, console bans (which are only for Wii Us), and perma bans, backup the emuNAND with that NNID, restore the clean (no NNID) 9.4 backup, create another NNID, backup that emuNAND with the 2nd NNID, restore the clean one again, and keep repeating the process until you have as many backup NNIDs as you want.
Just restore your 9.4 backup with the 1st NNID that you created when you are finished and want to use it.
I have not tested this yet, but this method should allow you to use emuNAND tool to create, backup, and restore NNIDs and switch between them.