If Snoke’s height is the issue, that can be resolved if the crew sticks one of those balls on a stick on a helmet Serkis wears so that anyone acting with him can look up at the ball as a point of reference for Snoke’s face, similar to what was done for Groot in Guardians of the Galaxy.
As great as it is to see practical effects in a Star Wars movie, not having Andy Serkis’ physically play a visually distinctive Star Wars character motion-capture style is an unusual decision.
That’s not to say this Snoke puppet won’t look impressive, but if Serkis isn’t the one performing the villain’s movements, it seems like a waste.