For those who have tried extracting hairs in GIMP or Krita using channels and/or recursive alpha adjustment, you'd know there will be moment where there'll be matte and they are difficult to remove. G'MIC would be the best place to put this due to its universality. Would it be a possibility that background match and matte cleaning come to G'MIC? It would solve the pain with hairs. Hairs extraction can be impossible with current open source software.