@Pandora Pretty much any command would be a huge cultural shift for the game in how it feels, but a command doesn't have to be on an opt-out.
One approach would be to not put responsibility on the party that feels uncomfortable, with not using a command to duck out in the +Iamreallynotdownwiththis or whatever, but instead to go entirely to a culture of affirmative consent. Say that every scene in public defaults to a PG-rating, and anyone wanting to take it to say, a hard R rating would have to do a command of, +okaytimeforadultcontent and if everyone codedly agrees, it's now an R rating scene and scene keeps going as private/adult/whatever. If they don't all opt-in, scene ends and FTBs, and they then do a handwaved, offscreen synopsis. If contentious, just arbitrated through dice.
I think virtually any kind of coded flagging for adult activity is going to squick at least some people out, because it says the quiet part out loud in a way that can't really be politely ignored very well or code going places where they feel it has no business at all going. There's a lot of really strong reactions to Haven, Firan's sex code and so on, and I think anything coded trying to establish boundaries for consent is going to run into that, as well as people feeling that it just guts the organic feeling of RP and makes something that's freeform and flowing into a mechanical hassle they don't want to deal with. That said, if you are looking for more of a MUD-like vibe of player arbitration to reduce terrible outcomes and prevent creeps from trapping people in miserable and deeply offsetting scenes, I think forcing affirmative consent is a strong avenue. And for a MUD-like, you can do a lot with say, tagging specific grid areas as very clearly having different defaults that are not PG, and or categorize what people are comfortable with. And filter people's 'No, Absolutely Not, Will always FTB if this is in a scene' categories with very awkward degrees of detail.
For staff, I think code like that comes down to whether you're okay with approaches that feel ham-handed, in-organic or controlling, that could scare off anyone that takes a look at commands and decides you're running a sex game and they want absolutely nothing to do with that depending on the degree of the commands and the sensitivity in implementation. Otherwise, it's accepting that creepers will probably pressure the fuck out of people and put the responsibility of saying, "I'm not cool with this" on people that might feel like they should go along with intensely creepy shit because they don't want to feel like they are being dramatic and making a big deal out of someone slowly racheting up the pressure on them, like they have to 20 other people, since boundaries are not clearly defined and consent is just assumed until someone sets their boundaries very clearly.