The corridor looks like those intended to be used for the cut extended bunker raid. It also resembles the one built for the scene where Vader was to choke Jejerrod (and I imagine it was taken from there as he is entering an identical lift to the one which gains access to the Emperor's chamber).
Vader all times appears to be the over glossy ROTJ mask (perhaps the actual meditation chamber is a composite of ESB footage I don't know what happened to that set after ESB but the Executor bridge set had clearly been only partially maintained).
For relocating Ben's Ghost to Tatooine the cave would be easier to add Ben to than my idea for Ben's Hut but it would lack that iconic storytelling touch (it would be nice if he eventually retired and died there giving Han another ironic line of prescience).
The main problem is while a shot like this might be relatively easy to do :

What do you do when Ben turns up?
You could have Luke talk to thin air for most of the time and only have him materialise when he sits down or I suppose you could use the back of Ben from scenes from ANH with the ghost effect until he get's into position to sit down.
It's a problem I would like to solve.
It's a shame we never got a view of the other side of the hut (which was never built anyway) as that would solve everything.