Verin may have been the third 'head' on the Supreme Council, but I think she may not have been as well. Given her age and genral knowledge I find it likely she was at least on the Supreme Council. However, I don't consider it necessary. Verin devoted herself to discovering all she could about the BA - and the BA is very arrogant in the typical AS fashion. I think she could have uncovered all of her information without being on the SC. Part of me doubts that Alvairin and Galina knew that Verin knew of them - perhaps this will be revealed later, but it doesn't matter much.

I really doubt that either Sheriam or Delana were on the SC - they are simply too young. Sheriam is a possibility due to her role as MoN, but that's not necessary.

I also can't help but go back to my old idea that MoN is position that the BA seeks to hold at all times for recruitment.