We are thinking of treating the packs the same way we handle the ANH Sandtroopers. Considering many Sandtroopers don't wear packs too.
For Sandtroopers packs are not required for basic approval, for level 2 they are required, and for level 3 they are only required if the on screen trooper you are emulating wears a pack. It will probably be more or less like this for the Mimban, but maybe a little different since there are so many variations of this trooper.