Gotta be honest...flat chested Lyn sounds more perverted than chested Lyn especially now that I've pointed out that they really are just an excuse to have Lolis in game given that they aren't biologically viable as a species. Also I don't think I've ever heard it mentioned that Lyn feed on nature, it says they are close to nature but not that they gain any sustenance from it. If anything Lyn seem to have exceptionally normal family dynamics which makes me think they probably reproduce exactly like IRL humans do, right down to the nursing process.
If you gave them proper breast options we could go back to pretending they are very youthful looking Gnomes and that the flat-chested ones are either not ready to reproduce yet or have some kind of Lyn specific genetic disorder that means they can't feed their young.
That being said you can actually give Lyn breasts with the right outfit and the maxed sliders, but I've always thought they just look 12 or 13 like that 14 at the very most. Because the only older teens or adults I knew growing up with chests that small were either having a slower time shaking off their childhood genetics or had that metabolism problem that makes you a gymnest no matter how much you eat or they were literal gymnests in which case they had sacrificed their chests to the exercise gods for the ability to do splits and cart wheels.
I went to an all-girls school too so believe me I know. Besides if your worried about the kind of perverts that want fully developed breasts...shouldn't you be more concerned with the Gon or the Jin or the Yun? I mean that Jiggle physics in no joke. Lyn only really need alittle bit added to their breast slider and alittle bit more added to their face slider options to create non-jailbait. I'm not saying make them like the other races but I am saying right now they are totally just here for 2 groups of people: The cute-obsessed and the pedophiles.
I'm in the former category, I like Lyn but I was just thinking about how they work the other day and I was like...wait a minute...how do they nurse their young? All I could think was...they don't. It was kind of like when I discovered that Lyn are one of the rare few anime based animal ear/tail wearers that definitively don't have human ears at which point I was like...how do the horned ones hear anything then? I try very hard to accept this race and it's shenanigans because I do like them but I can only stretch my suspension of disbelief so far you know?