Imp Fighter: I think the biggest problem would be the timing/editing of the shot, ie. will the edit come across as a jump cut with Vader just "appearing" on the pedestal (and miss the flow of showing Vader coming down the chamber steps and then onto the pedestal)?
While I understand you're trying to figure out how to make it so it appears Vader just entered the room and went straight for the giant "Emperor pager button", my main concern would be how it comes across visually.
I have to concur with Vaderios too in regards to the area behind Piett and Veers. The chamber has to be a figure 8 if you take into account the profile shot of Vader talking to the Emperor 
- the walls around Vader show Vader to be on the edge of the circular wall, not somewhere within the middle of a much larger room. This would mean that the meditation chamber would have to be to Vader's left, which can only mean that it is in a seperate room. This would also mean that the area behind Piett and Veers has to be altered to suggest an opening into the hologram room).
I suspect what they did was some typical cost-saving set manipulation (like how Ridley took the Nostromo bridge set, as well as some of the hallways, and converted it for the entire Narcissus section - the bridge turned into the shuttle and the outer hallways redecorated, ie. the Narcissus airlock was originally the kitchen). In this case, the above set is probably the same set the meditation chamber was in, but they removed it to create an empty room. But like with ALIEN, this causes problems when the nerds (like us) try to fit it all together...
If there is to be any sort of geographical sense of this, the area behind Vader would have to be altered to create an opening to the meditation chamber - the mediation chamber steps wouldn't need to be shown, as the foreground wall beside Vader could conceiveably cover them (though an opening would still have to be created).
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It would have to be along these lines:
either the area behind Vader has to be recreated to show the meditation chamber room (being that the pedestal he kneels on is about ONE FOOT away from the bottom circular step to his med chamber), 
as we should be able to see the edge of the step behind Vader's extended leg, or:
Vader has to be pushed back towards the edge of the wall to account for NOT seeing any part of the med chamber steps, much less the room that surrounds it. You would also have to add some sort of light source (on the airbrushed wall area above and behind Vader) or light "back wash" from the med chamber to help indicate the presence of another room and opening.
That is, if this really needs to be done... personally, I can see it left "as-is", with maybe some lighting backwash from the left area (to account for the med chamber being more brightly lit than the hologram chamber) and the area between the 2 columns behind Vader to indicate something of an opening.