Ooh, interesting thoughts! I think Valjean and Javert are among the Les Mis characters it would be hardest to genderswap (the Amis would arguably be easier, Fantine less so). I remember enjoying Stonecarapace's fic when I read it, though I didn't find it all that convincing.

I have an old idea of a genderswapped JVJ fic set in Ireland where Valjean runs from a Magdalene laundry where she's been trapped for years after being perceived as a fallen woman (agreeing to sleep with some douche in order to save her sister's kids? idk) -- she hates everything and especially nuns, but then some kind old Abbess teaches her they are not all like that, and she joins some convent where they have a school for poor kids and eventually becomes Mother Superior there. Unfortunately, Sister Obedience (Javert's nun name) gets sent there and she used to work in the laundry; the Mother Superior's sexiness lax attitude towards sinner is highly suspicious indeed...

It would involve a lot of historical research, though, and also Amis (who would be Irish independence activists), which is why I probably won't write it.