Just want to say, I hate the Qun as a concept. It is basically ridiculous. I don't understand why anyone would want to stay in a society like that, let alone join it for any reason other than sword point. It's fine if you happen to fit into their restrictions, but if you fall outside of those? You're going to lead a miserable life.
So my points were kind of being devil's advocate... and I think you're letting yourself be a little blinded by real Earth/Western beliefs. Some societies on Earth had the idea of a third gender, which goes to show you a binary idea of gender is not a universal one. What if the Qun has stuff built into it that allows the "mothers" or whatever to assign a person to a different gender? Those traits I listed are not all good for a farmer - a big, strong, ruthless, fearless female would probably be wasted on the farm, the Qunari need warm bodies for their war, so they might need to take the occasional female-turned-male. It can be spun to be consistent with the Qun.
I actually like them and I'm an anxious feminist. They treat people strictly but with care. No poverty, no hatred, no mistreatment unless you fight the Qun. Sexes, races prolly too, have different roles but they are equal. Qunari are ultimately racist, sexist and prolly ethnicist but they also fair. It is fascinating
So far everything we knew about the qunari demonstrated that their society is strictly gender binary. All the lore emphasisez men and women, their roles and responsabilities, differences. Even Krem identifies as a man, not woman or the third one. Heck, IB never states that qunari accept such people only that he does
A farmer needs to be bulky. Ruthlesness fits a benhassrath. Exceptional cases usually are still put in the the same branch but find their own unique place: cunning men become benhassrath or maybe strategy planner. Or maybe they study war as a scientists. A strong woman becomes a farmer or a spy. Etc
Systems like qunari's use biological aspects and differences between sexes, races and ethnicities. Also heritage. It is like advanced pokemon battle - where every pokemon species have a specific role and rarely anyone does sth new. Or animal breeding. Choice is hardly an option, efficency prevails
Though it wouldn't be the first time a retcon happened with threw all the efficency concept out of a window. They can build dreadnaughts but go into battle halfnaked despite what codex and Sten said to us. They also don't even have a word for their own race. Next time they'll probably declare that if a mage doesn't want to be a mage he/she will not be treated as such. DA lore and lore consistency don't mix, apparently