No, but am sure that the very fact that you are allowing "hidden shops" to operate with the implied possibility of "illegal activities" is sufficient enough to drag you in a court of law by some judge somewhere.........
Just saying, don't put your neck on the line if it doesn't have to be on said line.
Hidden shops are for users that only want certain people to be able to buy from them and whatnot. Almost like an Invite only store or forum even. Ophion is a marketplace tool, if people use it for malicious activities we cannot be held responsible.
The fact that illegal activities can occur in these shops is not under our control, there's nothing we can do to prevent them and that's what I'm going to leave this conversation at.
Ross Ulbricht wasnt allowed to use this argument in court, what makes you think it will work for you. Of course, you probably have no intention of building this in the first place.