Kumiho is boring because she was never anyone but Song Hye Kyo--I don't think I could find another woman who can look so completely crazy while smiling benignly.
Chimaera... had a lot of alternate PBs, most of which I can't see fitting her now, but I'd either go for Farrah Summerford, who is a little too hot for Martel but still has a dangerous, sorta feral look to her, or Peta Wilson, for an older version [not that it really makes a difference].
As for genderbent forms, I'd consider Lee Junki for Kumiho, though he's not quite wild enough. Martel is not, and will never be a male, and it hurts my head to even try to picture her as one.