I don't think separate shoulder slots would work well. Chest armor is already designed to handle that area. It would only really work with new gear slots going forward, it'd be too much work to go back and edit existing outfits to accommodate that kind of change. And then it'd just be weird and confusing having this new gear slot that only starts having visible gear in like, 6.0 forward or something. It's bad enough we have invisible belts as is IMO.

I wouldn't mind having some accessory options though that are tied to facial cusotmization rather than gear slots. So you can have things like eye patches or glasses without using up your helmet slot. This hasn't been an issue for me personally because I don't end up liking most helmet pieces anyway and almost always hide it uniless I am using an eyepatch or glasses, but it could be a nice feature for people that do use helms more.