While all of those ideas are cool, remember that it is most likely that all of the various alphabet agencys have watched these videos too. I know in some states, could be all by now, that hidden compartments in vehicles are illegal. I do know you are "supposed to" submit "accurate" plans when building or doing a significant remodel of a dwelling. I wonder if the day ever comes, how many houses will be destroyed looking for something that isn't there due to these videos.
the object isn't necessarily to conceal the existence of these spaces from the alphabet agencies, but more from casual visitors to one's home...in the event of a home invasion, it may possibly be a life saver. but you are right: YMMV