Honestly, I think every single companion should be able to be romanced, no matter whether it is malavai or khem val or scorpio or blizz. Who is Anyone else to say who I can fall in love with.
Er. And what if Blizz, or Khem Val, or Scorpio doesn't fall in love with your character? You know, romancing them agaisnt they will is kinda bad
I think that having companions who can't be romanced is quite good. This is life, you don't always get what you want. Not every person you like will feel the same way about you.