The project should improve the community and demonstrate leadership skills over your peers - which doesn't simply include Scouts. Involving only Scouts is actually the easy way out.
When you find a Scout who's able to involve friends from school, church, and the neighborhood, as well as other Scouts . . . that's impressive.
I think one of the best demonstrations of that was from one of my fellow Scouts. There were over thirty people involved in his project, and only a dozen of us were Scouts. He had friends from school, church, baseball, and soccer all there giving a helping hand. What would have taken the twelve Scouts almost all day to complete was actually accomplished in less than three hours through teamwork and everyone pulling together.