20 seems unrealistic given the longer shooting time per episode and actors’ wanting flexibility to be able to work on more than one project.
12-15 however seems very possible especially with the episodic format. Producing a longer season after the strike especially would seem wise. It would also allow Paramount to take a brief hiatus midseason (the way Discovery did originally) to stretch out the schedule.
SNW has already demonstrated that it is an ensemble show with a full cast that can basically carry or star in their own episodes. Not every main cast member needs to be on set every production day, and even the principal character, Pike, can step back in some episodes.