I remember another suggestion about hiding the access restricted menus and thats being fixed. I just checked my local development and it seems to be working. When all child menus are restricted from the user its parent menu is hidden as well.
Impressive!! I like that you’ve tried implementing it but let me show you the tastyigniter way of doing it ;).
The problem is, the value returned by $this->user->staffGroup() won’t always be Kitchen, Administrator or Cashier. However, tastyigniter uses the staff group ID of the user to check if that user has the right permission. I’d advise you check $this->user->hasPermission() to understand the logic of how TastyIgniter handles staff group permission.
Oh, and for hiding the menu, you don't have to unset the array, check out the navMenu method in the Template library, you’ll find $this->user->hasPermission() there :).
As i said earlier, what you have suggested was already implemented, but maybe i didn’t get you or theres a bug lol.