It would be better if we saw nothing of the hooded figure's face, then we might think it was someone else until Luke lifted his cowl (like Jason's Sidious hologram).
We have seen Sith on bike's before.
Who is this caped warrior walking so confidently into Jabba's palace?
In the holo message, on Dagobah, in Ben's place he doesn't wear the hood so for a brief moment we won't know who it is and it can cover problems like sticking Luke's head into shots that his body didn't occupy.
I made this montage of production designs for the Rebel Briefing Room/Command Centre, as you might be able to make out the actual set is in the pit in the middle and there is a clear roof open to space above.
I will try and work this into a more cinematic mock up but the gauntlet is thrown to anyone out there with 3D modelling skills.
