I love this idea! Lead with a story, focus on creating an idealistic story line that couples can relate to... feel exited about and justify to themselves having a stranger in their wedding. Make the focus of your website's and marketing pitch... stick to it, don't settle or try justifying yourself to the potential market - make it seem as if there is already an existing demand and solution by always having a story of how amazing it is to start a new with new friends, cultural growth and opportunities for friends around the world.

This is a two sided market place but you need to have weddings first.. once your content is there, lead with a story to travelers and target them through their appropriate social networks. it will be a lot easier to get people to join a wedding than it is for those getting married to invite strangers. - make them non-strangers first. always lead with a story, for yourself, for the joining and the to be wed - to learn about each other and the context in which they will meet.