I understand where you're coming from, but you've got a kind of 'three-body-problem' there: Just increasing from 2 to 3 greatly increases the odds against finding enough people interested in 3 simultaneous, different things. We need David Sawyer to quantify this. And, don't forget, interest isn't enough - each topic has to potentially promote argument, insults, indignant opinions and assumed superiority. So, for example, football - yes, war and remembrance day and Germans - yes, (looking good), ancients aliens on the history channel - nah. But don't give up yet; you have only to think up three likely topics and then worry about how to introduce them so they get the irritated reactions going. Then sit back and watch the fun. Think of yourself as The Puppet Master.