If Vader can beat Sidious and become a Sith Master at any time, why choose to remain the apprentice? That part of ghost prison I didn't buy was him getting sick. It's my headcanon until I get around to reading Darth Plaguies that the emperor is some kind of immortal zombie lol. I know that TCW goes out of the way to show vulnerability in count Dooku- situations like getting surrounded by the pirates and arrested, and attacked by Voodoo on Dathomir. I enjoyed how TCW handled Dooku, but I always felt like Sidious was on another level, and intelligent enough to avoid such unfortunate situations. Having stormtroopers used against the emperor is a good point, but they might have some fail safe built in to prevent them from killing Sidious (my speculation). Also, I always assumed that the Sith were only ones who could deactivate the droids, and it was out of the Neimoidian's hands. If not, isn't that a big hole in the clone wars plan? The Separatists could quit the war at any time. Finally, Vader and the shaft do ultimately beat him. But it is at the cost of Vader's life. My theory is that Sidious was distracted, and didn't perceive Luke OR Vader as threat that couldn't be easily handled with Sith Lightning. He didn't even use his two lightsabers for example, so it's like he wasn't treating them seriously.