Hmmmm...wonder why Beth didn't implement this since you can already glitch it somewhat?
I think it's along the same lines as dual wield, it was a late addition and wasn't polished for the final product. So instead of acting like it should ( kinda like the armed to the teeth mod ) it behaves like a bug/glitch, in which you need to glitch out ( force to work ) for it to work some what properly. I haven't tried any other types of weapons other then a glass sword and glass dagger( which only seem to work when it wants too ) and dual ebony axes( which work like a charm ).
Here's what I got done.... I have two ebony axes in my inventory and fav. list along with what I mostly use. I can now equip a dagger, sword, mace or any other type of axe in my right hand and one of
my ebony axes in my left hand. I then take off what ever it is I'm wearing ( clothing/armor just the chest piece ), the ebony axe is then shown on my right hip while naked, I then re-equip my clothing/armor and the axe is still shown on my right hip. Now I am free to have any weapon equipped in either/both hands and my axe is still shown on my hip, just like the pic I linked to that shows me with the headsmans axe on my back and my ebony axe on my hip.