I would have two suggestions for the outfit system, I know both have probably already been suggested in part, but I still wanted to make a post about my view on it.

Hide slots (Other than Helm):
First of all, I know people have been talking about an option to hide shoulders, I also would like to have that option just like you can do with helms, but I would also like that suggestion to be extended to all other slots at the exception of chest and legs slots (for logical reasons). Sometimes it's hard to get a good matching pair of gloves, shoes or belt or it would look better without having anything in those slots at all. Good example for chest pieces which have no sleeves, having no gloves or bracers would look better. Same thing for shoes where the pants are kilt likes (Mazzatun) or shorter already, having no boots, shoes or sandals at all would be a better fit. There's another bit that will also come up with my the suggestion.

I don't think that would be something really had to add to the game at all since it can easily be done with the helm and making it look like you just have nothing equipped at all shouldn't be too hard or a deal.

Monster sets / Unique looking pieces for outfits:

I know requests/suggestions have already been made for the case of monster helm and shoulder to be available as an option for the outfit system, where you can have the look of any helm/shoulders combo even if they are not the ones you currently were. This would be easy to track simply based on achievements for completing the corresponding group dungeon on veteran.

I would also like to extend that option for some unique looking pieces out there (even if some that aren't available anymore) to also have a place in the outfit system. Pieces I'm talking about , for example, the Encasement of Anguish, which used to be a drop from the rare Daedra Sisters Generals before dolmens were made to drop zone set pieces. This chest piece is the equivalent of the one available on the Dark Seducer Costume that already exists, but without having to use the costume, or its other pieces. I know there is also a helm that had the appearance based on the costume's one too. This is a piece that looks really nice in outfits but having to wear it, you have to sacrifice a set piece just for the look.

This would also including all the casual clothing you can steal from random containers, so you could have a nice casual clothes look. That would also fit well with the above "hide other slots" as you could hide the belt and gloves with that kind of outfit.

...Plus it might give people an additional reason to buy additional outfits slots from the crown store, don't you think?