I think (unless this is a side effect of having an old save) there's a bug when proposing a poly relationship to a second person if you already have a poly partner.
They'll always turn you down with the "not ready for this" text, even if all three characters have the Polyamorous and/or Open Relationships inclination, and even if all characters would agree to a poly relationship if they were single.
I love love love what you have done with this so far! Extremely addictive.
One minor thing I noticed: if you look at your partner during an encounter, their description lists what they were wearing at the start of the encounter rather than what they're wearing now. It would be nice to be able to read what your partner looks like naked - do they have body hair? Intimate tattoos or piercings?
Also if you have the Trichophilia inclination I've noticed it describes body hair for (cis) male genitals but not female during intimate encounters.
