In an idealized world I could imagine a SoP line containing the following:
Detectives: Allowed to wear whatever 'drip' they choose to and allowed to be as undercover or non undercover as they'd like, which should be fine since 1. It's only one person going full undercover, 2. It's limited off to a single person doing it during regular gameplay, 3. Detectives tend to be a step down during actual arrest protocols on a good day.
Security Officers: Drip is cool, we like drip, but one piece of 'sec gear' should be visible on their sprite. By default, any outfit should work as long as the iconic sechud glasses are visible. If you're wearing a mask, maybe enforce wearing a helmet or red jumpsuit or anything else easily identifiable by a visual look at the sprite and not *JUST* a shift+click. Going any further undercover should be fine with express HoS or Captain permission.
Warden and HoS: Keep them easily identifiable. They're command, they're supposed to be easily reachable. No need to ever really go full undercover boss when you can ask IAA's to undercover boss for you.
Responses to others comments and points below
Carthusia: "As for undercover officers: Its a legitimate tactic", I agree, I think it's a legitimate tactic, and that there SHOULD be some leeway and there SHOULD be incidents where it comes up. That being said, more than one officer at the same time makes antag players more paranoid, and honestly antags and sec should be easily identifiable towards each other on a usual gameplay level. Antags have to account for a lot of things. They shouldn't have to account for more than one undercover officer since that would be mentally draining. I think that trying to trick each other in terms of 'who's an officer, who isn't' might be adding too much of an extra level of thought, especially for our more casual antag players.
Landerlow: "I see no reason why this should be prohibited through SOP. If properly RP'd/played, it can add to the round. ", I believe that adding things into SoP enables RP and play, since SoP is usually kept to be an IC, roleplay thing in general. SoP aids roleplay. Other than that, the rest of the response is sort of catered around Landerlows suggestions with a couple compromises.
I believe every other response above me in the thread is taken into consideration?