It is very healthy to start a hackathon breaking te inertia of clusters of friends + silent newcomers. For Lyon we have already three new elements that we are trying for the first time:
* Buddies. We could ask all buddies to sit together in the opening, ask who hasn't got a buddy yet, and pair the remaining buddies life... as an excuse to allow a sample newcomers (the most likely to have no buddies) to introduce themselves to the crowd.
* A Welcoming Newcomers session where newbies meet insiders, right after the opening, before lunch.
* Main areas predefined (Wikidata, Mobile Apps, MediaWiki releases, Wikimedia Labs... probably Editing tools as well), which will be required to have activities for newcomers, and which will become the natural attractors.
In the middle of this, it would be useful to have @eloquence and @damons providing a quick inspiring vision of where are we on Wikimedia teh, and where do we aim to go.