If model A is adopted will students pay an additional SSAF fee if they take the optional semester? Will students pay a SSAF fee for three semesters in model B?

No. The change of the Academic Calendar would not affect SSAF Fees. SSAF fees for students are calculated based on your mode of study over the course of a year.  Fees are set for full-time students (regardless of the calendar), with a reduced amount for students studying less than a 0.75 load.