The only thing I see out of place is the icon doesn't quite match but it looks like a edited interface to me (although could be tq changed it again).
If the alternate equipment system doesn't work then it's something you'll have to code.
Handle the action to take when someone switches between sets, handle loading/saving equipment slots for it, make sure your gear calculations aren't using those alternate slots, etc.
It's a pretty basic system honestly but we can't offer much advice without knowing what issue you're having