I honestly wouldn't consider a fur chewer a "special needs" chin, but that's just me. They don't need any sort of special care requirements over a regular chin. They don't need more toys or a nearly silent environment with music playing 24/7 to keep them happy because they're going to chew no matter what if they want to. They also don't need to be kept alone and isolated. Just because they chew doesn't mean they can't be housed with other chinchillas. (I mean this for same-sex pairs, not your male/female). They may or may not chew on their cagemate, and if they do, the cagemate usually just sits there and lets them. It doesn't hurt them, just makes them look weird.
As far as bringing a female into a house with two bonded males, yes it can start problems. It's been my experience that males will continue to get along when there are so many chins it doesn't matter, or the females outnumber the males by a good bit. I have two males housed together, and when I only had 3 females, they would have issues when one would go into heat. I'd trim whiskers on the dominant one and that would work (though it doesn't in every case). However, when I upped to 4 females, the hasseling stopped, and now that I've got 6, my males are fine. So, if you're going to bring a female into a house with two males, be prepared for issues that may arise.