This issue seems to be much less of a problem than it used to be. Our groups mostly seem to have found ways to accommodate the "pure addict" through open meetings, and most meetings/groups confine themselves to the singleness of purpose. There is not much conflict at the moment. The key things are that we cannot confer AA membership on a non alcoholic.
The book, on page ninety, does give us some responsibility on this, suggesting we satisfy ourselves that the person we are working with is a real alcoholic.
On the other matter that you raise, illegal activities, the AA book suggests we keep our sharing "general" for good reason. Not only may the wrong people be listening, but I have seem situations where a newcomer says things he later regrets and that has had serious consequences at times. People have been arrested for what they said at an AA meeting.
In terms of an members finding AA more stable, we have the same thing here. We have some very neat na people with good recoveries attending AA open meetings for this reason. The sad fact is that part of the reason NA is a little wobbly is that many of their recovered members are hiding in AA. NA needs them. Their presence in AA probably does more harm to NA than it does to AA.