I can't imagine any universal criteria of what could be considered a secure space that could be applied programmatically to the tens of thousands or hundreds of thousands of roomsThis could be an issue but I am honestly not sure how much of an issue. MOOs use an inheritance system so a lot will depend on that family tree. It could work beautifully or not. Also, every room will have props and verbs on them. It may be possible to use the presence of these to classify rooms. Some might need to be manually classified. I honestly can't say how intensive this might or might not be. I figure that if staff likes any of what comes out of the discussion they'll know if it's practical to apply or not.
subjective opportunities to players
I'm not sure if I understand this. My understanding is that this is not subjective. My understanding is that you are either dealing with a place where you have to xhelp and get approval for crime or you aren't. If staff has decided that a given location is considered secure and needs xhelp approval for certain actions, I feel that this should be communicated as clearly as possible to players with as little room for interpretation as possible.
@crime command to distinguish whether sometihng might need xhelped about in certain areas
I kind of love this idea. It allows for more information to be passed along as well. If it's a secure area on gold the output can specify what actions need xhelp approval for example. Plus you can target a command like '@crime here' or '@crime door'.
High security cameras and sensors scan your every move in here
Personally not a fan of this kind of thing. If there are ameras or sensors then I feel there needs to be actual cameras or sensors there. If there are guards there then I feel there needs to be NPCs present. Just my preference.