I think like the promos they are giving they will show crime increased in Mumbai so new members required as such.
People keep guessing who of 12 will be present today. every member will be switched btw Friday and Saturday. I think It will be all random no rule. So all get chance to perform and show there acting.
Just see this way Now we have 8 members--1hour
Then we have 12 members-2 hours.
Each will get more screen time to perform.
They tried but couldn't give enough chances to Vivek, Freddy and Tasha.
So they thought this way.
A randomly who will be present in Friday or Saturdays or on both days. they will decide according to plot and availability of actor.