Rabbi Ovadia Yosef z’tz’l ruled that a woman can read Megillat Esther for a man l’chatchila,”
Women and men have EQUAL achrayus in hearing the Megillah leining, l’chatchilah. Women have NO achrayus to put on tefillin. My understanding is that when one has a chiyuv in a mitzvah requiring both an active and passive participation (i.e. Kiddush, Havdalah), that person can be Motzi another person with the same chiyuv. But it has to be an equal chiyuv in order for this to be so.