Provided no face-to-face interaction happens, Star Trek: Discovery could pull this off quite easily without risking alienating fans with a poor Spock casting.
It sounds like, at this point, Star Trek: Discovery is not looking for a new actor to portray Spock but at the same time not ruling out his presence.
So how could they do that without pretending Spock is in the bathroom every time Burnham and Sarek are on the Enterprise?
The move would also be appropriate, as canon has shown Spock and Sarek’s relationship at this stage to be very strained after Spock went against his father’s wish that he join the Vulcan Science Academy and instead joined Starfleet.