Nephthys
The Gr8est!!!!!!!!
The only way your scenario would work, HWKA, and please note that without a single one of these the whole thing collapses, is if:
1) Luke and co somehow manage to track down the Emperor via their intelligence network, even though they don't have nearly the skills to match the Empire or the Emperor on that front. Also, they're fighting a war while doing this.
2) He doesn't move, catch wind of them or do anything on his end.
3) They manage to get close to him without any hiccups. They have to be perfect. Note that they'd have to be being a LOT more competant than they usually are, power-wise and intellectually.
4) They assassinate him. They have to be perfect.
5) They get away. They have to be perfect.
6) Palpatine, out of his numerous corps. of dark jedi clones etc, for some reason chooses Droga again to house his spirit.
7) Droga, feeling Palps death goes insane and slaughters his crew.
8) Droga just happens to be aboad a ship at this time, he just happens to be on a planet, he just happens to accidentally smash the bridge controls, he just happens to crash the ship, the ship just happens to not be spaceworthy or have any communications etc afterwards, or other ships or escape pods they could escape in.
9) Prestage ****s around instead of looking for Palpatine. Make up a reason.
10) Palpatine, in the midst of a war, fully knowing about the threat of opposing Force users did not give any instructions of what to expect if he succuums to the very real threat of assassination.
11) The Empire splits.
So basically if God or George Lucas made it happen. 😬
edit: You may think I'm just being facescious or whatever but really, without any one of those unbelievably contrived circumstances your plot fails. So you can understand why I'm really not even going to award them a point for it:
9.5/10 Empire wins. The 0.5 is for if something just rediculous happens.