the reason it being all grouped in "Others" is due to development constraints. Rather than structuring entirely new LI paths like in place for the main 5, you can use roughly the same selection of events in the "others" path, and end up with a given girl fulfilling certain conditions.
I for one, am now fully convinced a Lily ending existing is inevitable, given that she's about the only female in the whole game with an actual plan and endgame of her own. Camilla / Riona will be another, although I can also see an ending for them that ends with "BFFs becoming lovers" type. Quinn will most definitely have an Others branch for her too. Beyond that, probably not. None of the other females in the game occupy what I'd call "development space consistency" to justify specific MC-related endings for them.