My next suggestion is to have male lamia be called naga instead since it would be more correct that way. Female/futa could stay as lamia, naga would only be male and lamia could ony be female unless modded in the lab.
Nereids too should be female/futa only. Maybe their male version should be called Tritons or Mermen, I don't know.
True dat just like harpies should only ever be female/futa starting out.