Okay I think I do know what I would do if I wrote faunus Ruby now. Although I have no intention to since I'm already writing a fic and I shouldn't be writing fanfiction at all anymore.
But I'd make her a spitting cobra faunus, and the story would eventually be Whiterose because I love Whiterose and wanted to write Whiterose at some point anyways and any Weiss x Faunus story has the potential for interesting drama.
But it would be a three act story:
>Summer was a faunus
>After she dies and because there are no faunus on Patch, Tai wants Ruby to get to know faunus better and be more connected to "her people"
>Takes the family to Menagerie when Ruby is like 7 or something. She meets Blake, Ilia, some others, and stays in contact with them
>As she grows up she becomes more involved in faunus rights, protests, and White Fang activity despite Tai and Yang's concerns.
>Weiss goes to Vale around when Ruby is 13 to perform in a charity concert
>White Fang sabotages the concert but Ruby becomes basically infatuated with Weiss after hearing her sing
>A year or so later, the White Fang come up with a longform plan to kill Weiss, infiltrating Atlas with someone who will pose as a new worker in the Schnee mansion
>Ruby and Blake talk Adam down from killing to kidnapping, and Ruby, after saying goodbye to Tai and Yang, fully joins in with the White Fang and gets set up to become Weiss's new maid in Atlas.
>Second part of the story is the two of them living and working together, as Ruby gets to know Weiss more and Weiss develops a crush on her in turn while being oblivious she's a faunus and White Fang.
>Third part of the story is the kidnapping and the truth being unveiled, Ruby in a moment of reflexive anger after Weiss says something racist and hurtful to her spits venom in Weiss's face, blinding/disfiguring her left eye
>Eventually they'd still love each other and Ruby would sabotage the kidnapping but not sure if they'd stay "together" or if they'd part in a sort of tragic romance because they know it wouldn't work.
>Maybe Ruby goes back to the mansion with Weiss because she's in danger with the White Fang now too
>Maybe Ruby takes Weiss back to Patch to hide and reconnect with family
And the story would end around there. Obviously some gaps to fill but yeah, that's what I'd write.