spoilers:end of spoilers Hope works better in the Phoenix trinity that Maddie did as seen below.
Louise was a redhead right? I wonder if it may not be easier to retcon Louise as being a lost piece of Jean when Jean/Phoenix was split apart after the events of Endsong. A bit like the main Jean who was living a normal life as a waitress in Phoenix Resurrection. Otherwise I wonder why Jean would impregnate a random woman with the child of the Phoenix. As you said, with Rachel it makes sense that she would do that to herself. I have to admit that Hope was never a character I cared much for, especially after Marvel endlessly teased her connection to Jean and it never paid off, until perhaps now. I'd have a much better opinion of her if she's in fact Jean's other daughter besides Rachel.