Q. Who was it that successfully agitated for women to be allowed to undertake extra mitzvot?
There are actions which are commanded and actions which are prohibited. The second category is basically the “thou shalt nots” of the Torah. These apply to men and women equally; though there are a few cases in which womanness makes a difference, for example in regard to not cutting the corners of one’s beard.
One cannot argue that “thou shalt not kill” applies to men because they are men but not to women as women. Killing is wrong, period: wrong if the killer is a man and wrong if the killer is a woman (though halachah distinguishes between them insofar as a female sentenced to death has extra rights to modesty when it comes to the execution).
The male/female distinction applies to “positive mitzvot dependent on time”, which were not obligatory upon women, though they were duty bound to observe some such mitzvot (Kidd. 29a).
Those that they did not have to observe were not prohibited to them but they were exempted, and at some stage women wished to undertake some such mitzvot (e.g. hearing the shofar) waived their exemption. Who those women were, and whether they struggled to find acceptance – that’s a question for the historians.
Though there are women who have shown an interest in the mitzvot of tzitzit and tefillin, rabbinic authorities have not been in favour and there has been little female interest.
Probably the most visible mark of increasing female involvement in Jewish observance has been in the field of Torah study; there are now many learned women who can handle Jewish texts with great competence.
Amongst orthodox women there is little real interest in becoming rabbis, but our value system always regarded scholarly substance more highly than communal rabbinic office.
(See Saul Berman’s “The Status of Women in Halakhic Judaism”, in Tradition 14:2, 1973.)