It seems pretty clear to me that J.J.'s ideas -- particularly relating to Kylo Ren's ultimate arc -- are contingent upon there being a "bigger bad" above him. Since Johnson axed Snoke, Abrams scrambled and contrived a way to get the Emperor back in there to occupy the basic story function that Snoke otherwise would have had he not died.
Put another way, I think Johnson beat Abrams to the punch in terms of the Kylo/Snoke resolution, only he didn't take it as far as I expect Abrams will.
In doing so, Abrams will run the risk of opening himself up to more "You're just ripping off the Original Trilogy!" criticisms if it's not handled well.