After the shower of video game quotes that Final Boss "whatever" skin (I forgot his name) A simple Fate/Stay Night skin wouldn't hurt too much.
Quotes are one thing, a blatant skin is another. Lux is a nod to Marisa, but she doesn't look like Marisa or talks like Marisa.
Having Riven look like a hair dyed Saber is just placing a "please sue me" sign on your face. If one of Riven's alternate skins had some weird quote about a holy grail or "Heroic spirits" Riot could say any number of things of why the quote could be about LoL and not Fate stay night.
