AFAIK, there is no such mod yet. I personally go to 3rd person, turn the camera to face my character and then go into inventory - equipping is reflected in realtime on character.
Something that works like when you view an item close-up, removing the UI windows, but without showing an item of course, would be a good solution I think. Probably easier to implement as well, as I imagine getting the PC to show up in the menu itself is tricky.