Hi, yes I can not see why you can't change the the towbar from fixed swan neck to a detachable, you will have to unbolt existing and fit new detachable bar which is available as a separate part, existing OEM electrics would remain in place (all I would say is I am unable to say 100% the electrics will reach the socket bracket on towbar as I have never changed one like this before, however you would be very unlucky if the OEM electrics did not reach as it is the same Towbar in theory.
My advice would be to go on the Westfalia website and search for the nearest Westfalia dealer local to you, they could order a bar in for you and might be open to sending it back (you might have to pay carriage costs worst case scenario to send back) if it did not fit with existing OEM electrics (in my opinion it should work though, let us know how you get on)
Hope this helps