I'm sorry but sadly you have to be a council member. Spell casters do automatically give you council position, however spell casters from me being in there doesn't always give that coven vibe feel.
However in way, I think it's best for members to join a coven and automatically have to work for council position. With that work when we reach it, we end up easily knowing more, but if we don't have to work for it, there's a risk that there will be fluff.
Simply said, spell caster automatically puts everyone to council position. You may learn, but in other covens you get to learn, build friendships, and you also get to work for things you want.