As far as the federation coverup side of things, I'm almost certain we're going to be hearing more about that in further books. If you resolved that here, we wouldn't have much to talk about for the next three novels.
On the Cardassian side of things...the sad fact is, Cardassia would [and has] chewed through anyone who was of that character. The noble, 'federation ideal' type just is not going to work on Cardassia. At least not yet
. They need someone who has a hope for the future, but at the same time, is smart and cunning enough to keep from getting murdered. That is pretty much Garak exactly.
As he says himself, what Cardassia needs is for someone to sit on the chair, and keep democracy going for the next generation. By then, maybe someone that good can take over, and things will change. Maybe they'd even join the federation.
But that's all future stuff. Right now, they aren't there. There are forces actively working against those ideals. And it isn't just a select group of people either. Its the remnants of an entire generation.
Personally, I think as far as Cardassia went, things ended on a high note.