The Church (and by that reference here I mean the ORTHODOX Church - western and eastern) prevailed over a persecuting Roman class in the 4th century not by being credible in this sense of "acceptable" but by the blood of the martyrs - as Tertullian characterised this, "the seed of the Church." "Credibility" has much more to do with faithfulness even unto death than with being acceptable to the mores of unbelievers.
If the Orthodox Church was ever to have women bishops it would not be because it felt that it needed to conform to a secular world view, perhaps that shared by David Cameron, the British Prime Minister, who later opined in the House of Commons that the Church of England needed to "get with the programme." No, it would do so because quite independently it believed it to be God's will to do so in conformity with Scripture and Tradition and in the unity of the Church. There are many in the Anglican Communion who honestly hold to that position (albeit that Orthodoxy respectfully disagrees with their conclusions).
The lesson I take away with me from this sad affair is that Christians generally should seek credibility from the gospel rather than court respectability and acceptance in the eyes of the world. I don't expect that position to be popular or to make it easier for people in the short term to receive the gospel. But, will I sacrifice the gospel for a substitute secular standard of belief and witness? No, I will not.
So my argument is not with those who support women bishops on theological grounds (however much I might disagree with that position, and I do) but with those who believe that such issues should be addressed from outside the Church and according to contrary, extrinsic principles. Therein lies the authentic question of "credibility."