I think nation and cultural identity should be the main theme and metaphor of Inhuman books. It's what would set them apart from X-books.
Inhumans, particularly the NuHumans, can't really escape from the whole feared for being different thing that used to the define mutants, but by focusing on them as a group of people who just discovered they don't really belong to the society they have been raised in and that instead they belong to this weird Inhuman nation that has its own culture and traditions would provide for some interesting stories.
Inhuman books should explore the cultural clash between traditional Inhumans and NuHumans. The Royal family would be trying to make NuHumans part of their society but NuHumans wouldn't really fit in, some wouldn't even want to.
I think having Inhuman books focus on this cultural clash would be more interesting than exploring the "hated for being different" as a metaphor for racial and sexual identities, that should be the X-men's thing, IMO.