I'm glad the general consensus is that Bona is a way better concubine candidate. Zenjiro's logic is very...him, but he doesn't seem to consider how she'd actually be quite content if she married him.
Girl just likes doing her work-hobby, and being attached to the Capuan family would absolve her of many fussy responsibilities getting in the way of that. Not to mention she gets to be up close with the cutting edge marble technology.
Freya jives quite well with Zenjiro as a potential wife for the exact same reason. He already provides her with everything she wants to be happy; in being himself, he happily allows his concubines to continue being themselves as a given.
Case in point: allowing her to confiscate the space-isolating barrier tool while on her ship. I bet Aura doesn't like that, but Zenjiro was able to see it from her point of view rather easily.