A twin axle with a walk round bed and a reat washroom, cant think of a mode like that.
We have a Lunar delta 640EW which is a t/a , rear full width washroom and fixed o/s bed.
The models with a walk round bed that i have seen have the shower and toilet in the centre of the van, toilet one side and shower on the other.The side bed isnt a drawback for us as it gives us the luxury of the full width bathroom. Also on ours we have the solid partition between the bedroom and the living area, which at night closes of fully giving a snug bedroom, some of the newer fixed bed models just have a plastic folding door and a flimsy blind.
Drawbacks to a t/a van , the only draw back that I have encountered is manouvering the van when of the car, although i find reversing the t/a very easy, especially eith the auto box. I am sure that there will be a posting very shortly to tell you of the benifits of s/a vans and that twins are not needed.
Your Sorrento should have no problems hauling a large twin (we looked at one a few years ago) , look around any camp site and the sorrento is probably the most favoured tow car.
Moving the mover from a single to a twin, depends on the mover. we has a heavy duty power touch fitted to our single axle which fortunatley was able to be transferred to the twin, but I had to get a new control box from powertouch. I believe though that this is the only mover which is transferable. As a thought the mover is at its limits and is slow but does move the van, if cost were not a problem i would have opted for an all wheel mover.
You dont say if you are looking for new or used, but have a look around dealers and see what suits you.
A used model which is prety rare and unusual was the Lunar delta 620. It has a rear fixed bed toilet and shower in middle and living at front. the bed is widthwise . Pretty rare to find though