Way back in third world countries, sisters that were pioneers will go to places without a congregation; as soon as possible they will start a small group. They will conduct meetings and eventually do all the duties normally assigned to brothers, the only thing that they couldn't do was participate in judicial matters; this arrangement continued until they had baptized brothers qualified to take over.
It was common to have sisters in formal congregations doing the duties of assistants or MS; most of the time they did a better job that the brothers.