Very interesting thread.

In the past, a consigliere was elected by all members of the Family based upon respect. They functioned as somebody who could be relied upon for advice and counsel. With a few exceptions, he was never appointed by the boss. Therfore a boss could not strip him from his rank unless the capos and soldiers of the Family demanded it.
The consigliere was a buffer who protected the common soldier´s interests and he served as a liason between the Family´s members and the boss.

A consigliere was also responsible for maintaining the Family´s money fund. This money was loaned out to members when they were in trouble with the law or for business purposes.

I don´t know how this position functions today. But I suppose when the old mafia tradition got lost, the role of a consigliere changed. It seems that today, it´s just another rank.