Dunno how to fix my book; might just declare victory and go home

So I took my two weeks, and I reread THE LONELY YEARS, and it still has one very specific problem I'm not sure how to fix. The problem is that the main antagonists of the piece--the roommates of my protagonist--seem a little underdeveloped and, more than that, not entirely in tune with the problems that my protagonist is dealing with. It's hard to explain; there's just something subtly wrong about the way the pieces fit together. I wish that their conflicts more closely mirrored my protagonists' conflicts, without everything dovetailing too much.

The problem with fixing this is twofold. One, the book is pretty tight right now. Usually, when I want to revise some part of the book, I find that my subconscious has conveniently left an empty space (usually an underdeveloped plotline or character) who I can turn into the solution to my problem. But here I'm not seeing anything.

Two, remember a few weeks ago when I said that style determines content, I just feel as if maybe the style of this book, with its claustrophobia and close focus on the protagonist, means I can't get into the other characters' stuff as much as I want to. As I tried to think about how to expand their role and get deeper into their heads, I just started feeling like all the possible solutions would hurt the rest of the book.

When it comes to editorial feedback, I'm very wary of the kind of feedback that I call 'golden mean' feedback. It's where the critiquer says, "I love that the book is this, but can it also be not quite so much this?" It's just a truism that the thing in the text which is most distinctive is also the thing that'll elicit the most criticism. And, knowing this, the critiquer or editor tries to head off that criticism by finding a version of that thing which can't be critiqued. But sometimes you're just doing the thing! If you're writing a science fiction novel that's about a relentlessly grim dystopian world then it doesn't matter if the character also has a cute puppy, because to the extent that the puppy alleviates the grimness, you're undermining the point of your book! Now would it be nice if the book wasn't such a downer? Yes, theoretically, but that's what the book is!

Similarly, would it be nice if my book had a more expansive and even-handed view of some of its themes? Yes, but then it wouldn't be so lonely and claustrophobic, so what can you do?

My answer is (probably) nothing, but I've sent it out to some friends for their comments, so we'll see what happens!