None the less, their characters don't come across to me as fighters.
They simply don't fit the archetype.
Irene has a long history of playing the victim. Ayame has no relevance to the story whatsoever anymore, and her role has always been to sit around and do nothing in the village. Miyako would be the only wild card, and she has virtually no character development to begin with. It would be pretty sudden.
They don't really come across as fighters to me either. I'm just saying you can't rule them out, altogether, as being possibilities to consider.
As far as archchetypes go, yes Irene fits the victim bill pretty well, historically speaking. However, there is another archetype... The kung-fu hero. In many kung-fu movies the hero is a victim at least at first, then he has his aha moment where he says, "enough is enough," and trains with the old master until he's good enough to defeat his persecutors. Irene Lew may very well fit this archetype as well.
Ayame does seem to fit a more subservient role, but then again she is the wife of the patriarch of a ninja clan. She probably has been trained. As far as re-integrating her into the story, I don't think it would be all that hard. Three of her children are already involved. Chalk it up to motherly concern and there ya have it, folks!