Okay, I actually really like Palpatine as a Sith Crystal and Snoke as Cultist leader, together with RogueLeader’s ideas regarding Rey embracing who she is, these idea would also keep the climax from being “Jedi kills someone”, touching I think, on all the aspects of what it would mean for Rey to surpass the Jedi.

Along the lines of Rey embodying the best of and surpassing the Jedi, Rey seeing through the Crystal by embracing the WHOLE force would give meaning to the opening epigraph in the TFA novelisation:

"“First comes the day
Then comes the night.
After the darkness
Shines through the light.
The difference, they say,
Is only made right
By the resolving of gray
Through refined Jedi sight.”
―“Journal of the Whills, 7:477”

(Which I always wanted to see in TFA instead of “A long time ago in a glaxy far, far away…”)