What a neat idea! The only thing that pops in my brain, at the moment, would be to work on things in themes...

such as if the sermons were geared to a theme...maybe monthly, or quarterly, etc...
then you could meet in groups to do things pertaining to the theme,
where you could actually schedule activities, games, or what have you, Group discussions, all based on the theme.

With lots of participation, discussion, and new ideas of how to apply the concept, you might see a change in people...that is the only thing I can think of at the moment...