There is a PER base for S/Os. Not sure of the numbers but suspect up to 40 based on the numbers of Captains and F/Os required in PER.
They have S/Os operating on some of these domestic services so that they can do their 'check to line' flight. Many of them have been on training wage awaiting the first aeroplane so that they can actually check out.
Once normal line ops start I don't reckon you'll see S/Os on the MEL- PER- MEL sectors. Simply no need for them.