I assumed MurderBot would not look male or female but look androgynous. Additionally the merging of machine and meat would result in thin limbs, likely they are going to have to do a lot of CGI work in post.

Casting a big name actor in the role, especially a male actor who tends to play tough guys, seems like a mistake. ~80% of the murderbot fans I've talked to, decided they weren't watching the series when they heard that casting decision. Generally the take was: "if that is who they cast, they don't understand why the books worked." I reserve my judgement until the series comes out, actors can act and should not be cast based on audiences expectations, but it does not auger well.