The special environment slots hold your special outfits that allow your character and its boffs to operate in such environments, automaticly switching to them when you beam into the mission. And back when you beam out again.
Also the characters physical statistics should be looked execpt for the undercover slot. It makes little sense that when yu want to change into your beachware you can also chnage how you look, including body mass and size and other things.
Undercover uniform can only be change in a med bay, reason is that in the show character going undecover nearly always change their appereance to fit better into the environment and that was done in the med bay.
And finaly the holosuit slot lets you wear anything you want, but its restricted to actual holosuits, should they become part of the game one day.
I like my uniform each which makes perfect sense, I got some normal duty clothing, I got some workot clothes, I got dress clothes, I got civilian clothes for the black ops, for a nice party and last some nightwear.