There are some new costume parts in the i25 client, I've noticed. I'm sure more mods are not far off, even if they don't become "official" content. But I wouldn't set my expectations too high. Each part of the costume has a "slot" it fits in, and there are only so many slots to choose from. Putting new textures in the slots that already exist might not be too complicated, thus we have carnie corsets and yakuza tops, etc. But adding a second "slot" to the "Shoulder Detail" section to accommodate separate shoulder armors is far more complex.
It was done once before when tails were taken out of the "Belts" section and given their own slot. Possibly before that as well, but that would have been before my time in game. I don't know what it entails. It might be cake or it might not even be worth thinking about.
There are a few things that I think might be accidental or oversights. I don't know why tech knight wouldn't work with bare skin. I don't understand why most of the gloves are unavailable for trenchcoats even when you pick the short sleeves. I know some things they restricted due to nasty clipping or other glitchiness, but some of them don't really make sense to me. With any luck those types of things are easier to deal with and can be remedied.
All that being said, and as much as I loooooooove costuming, I know the people working on this have waaaaaaay more important things to deal with getting the servers stable and the gameplay bugs worked out before they start dealing with vanity. So patience. ;)