Get rid of the Death Star II. Instead have the final space battle be centered around the construction of say, another Super Star Destroyer like the Executor. Empire is building something important but not as large scale as another DS, Rebels send Fleet, and a large number of Imperial ships jump out of hyperspace and ambush them. Emperor is aboard Super Star Destroyer beig constructed.
By "original plan" they mean one of many varying possible plotlines. I'm pretty glad that the original trilogy wasn't extended into 9 movies focusing on a character that barely had any significance to the series.