Response to an unknown guest
Isaac Clarke? I could see Ironwood hiring him as an engineer, just like he was in Dead Space. He would do well, working in Atlas. But once shit hits the fan, I think he could answer the call to duty, just like he did with the Necromorphs. The only way I could see him standing a chance against the Grimm is if he had all his engineering tools/weapons at his disposal. I could see the main cast being sorry for him, maybe even Ironwood would find it inspirational: doing what he had to do.
I know who Carver is, but I never played Dead Space 3. All I know is that he works with Isaac and helps him fight. I'm sorry, but I don't think I can answer your question about him and Harriet. But if you see a resemblance between them, given what you told me, I guess its possible.