Re: Janskeet's freezing chamber posts.
It's possible that the Executor might have something like a freezing chamber (it's a big ship and the process may come in handy) but it adds layers of unnecessary plot complications to wade through.
Does the duel between Luke and Vader take place on the Executor?
If so how does Luke escape?
How do any of them escape?
Our heroes only escaped the Death Star because Vader wanted them to and he really wants to capture Luke (the whole film has been about this).
Also the Executor is at least as big if not bigger than Cloud City so the mock up is really out.