AviK: Stop it. Your distortion of sources is just bad now.
1. That is not what the Gemara in Bava Basra says. The Gemara says you have to do anything possible to avoid a non-Tznius situation, but if in the end of the day you’re really stuck, then it’s an Ones so it’s okay (you could have quoted the Gemara properly and it would have served your point, but you chose to misquote it).
2. Evah doesn’t apply to by Jews, it’s an outbreak of Pikuach Nefesh, and we are Mattir D’Oraisas in some cases because of that fact. You bringing up those sources is both incorrect and irrelevant.
3. I don’t think that’s what the Sridei Eish says but I don’t know that T’shuvah by heart, so I could be wrong. What does “singing for enjoyment” even mean?
4. That’s the Sridei Eish’s Chiddush and yet he still doesn’t Pasken by it without the second Tzad Lehakel that it be Devarim Shebikdusha, over which the Yetzter Harah has no control. Presumably he didn’t hold of this by itself based on the Gemara in Rosh Hashana (I believe 27a).
5. The singers know that Frum people won’t want to listen to women sing. It’s not embarrassing them if they put you into an impossible situation, with full knowledge of what will happen.
You should have said Ee Efshar V’lo Kam’chaven and been done with it. That would have been a valid Halachic argument and quite possibly is correct as well. Your attempted distortion of sources does nothing for either you or your argument.