In light of the recent and ongoing conversation within Orthodoxy about ordaining females as rabbis, one of the most important and initial things to consider is what a female rabbi should be called. Some suggested Rabbah. Here's a quarter-century old suggestion for Rabbati in an article called 'How About Rabbati?' by Werner Weinberg in 'Journal of Reform Judaism,' Summer 1986. Ashkenazim might try Rabbosi on.
Interesting points: Weinberg discusses the etymology of the term rabbi and it's English pronunciation. He likewise suggests that Rabbati be vocalized (in English) with the same i pronunciation, although he admits that it doesn't sound very nice. To me that sounds like a lazy call for zimmun.
Incidentally, I recently noticed, with pleasure, that in the de Sola Pool siddur רבי is vocalized the following way in Pirke Avos, רִבִּי. However, for Rabbi Yehuda Ha-nassi it is רַבִּי! See this post for Revi Ya'akov Emden's position which justifies רַבִּי for Rabbenu Ha-kadosh alone.
In the 18th century Rabbi Chaim Yoseph David Azulai famously termed them Rabbanit.