I've made a lot of "action" optional already and I never intended to do that. The initial draft was a lot more straight forward than it is now. BM is actually just a "let's get a feel for this developing thing before I start something bigger", so I always wanted to keep it releatively simple and yet I've changed as many routes as I could change without completely rewriting the story. Now if I'd make the Ellie content optional, the story wouldn't make much sense anymore, so it'll have to stay the way it is.
Maybe I'll find a way after the game is finished and make an addon for it, but until then it'll stay how it is.
By the way my goal was always to make Ellie look cute and young, but still old enough to be adult, I've even googled 18y.o. for reference (you don't want to know how many porn popped up, it's really hard to find non-porn pictures, lol), it's part of the story, her looks is meant to trigger a certain feeling in the player (and no, not the one you got xD), she's meant to be the type of girl you'd never let get harmed in any way or by anyone.