In general, hierarchical Christian religions of the sort that have bishops do not have very high ranking positions for women. So, if you want a piece that is a high-ranked female religious figure that fits with bishop, you're not going to find one. Alternatives include using a neologism like Cardinaless or abandoning one of your requirements for naming the piece. Mixing religious titles from very different religions doesn't work well, because Christianity, from which we get bishops, doesn't easily mix with other religions. Diagonal moving pieces do not always have religious names. For example, the Queen moves diagonally but doesn't have a religious name.
In general, hierarchical Christian religions of the sort that have bishops do not have very high ranking positions for women. So, if you want a piece that is a high-ranked female religious figure that fits with bishop, you're not going to find one. Alternatives include using a neologism like Cardinaless or abandoning one of your requirements for naming the piece. Mixing religious titles from very different religions doesn't work well, because Christianity, from which we get bishops, doesn't easily mix with other religions. Diagonal moving pieces do not always have religious names. For example, the Queen moves diagonally but doesn't have a religious name.