On nice weapon mods!
In this shot, if you look at the subclass icon, you can see the spots for the other two subclasses. Given that the spots for the other items are only there for the ones filled (like only one extra ghost, but six power weapons), suggests that all three elements might be present. Then again, the layout isn't the same for the subclasses, so maybe those boxes are just background (they seem to match in color and shape though..).