Tell him to "Go Big, or Go Home..."
I built a softball backstop, with the help of a contractor, for a church for my Eagle Project. Seriously though, have him look at bridges, benches, trash can holders, etc... Things that they can do pretty easy and with minor tools. He will have to submit a plan of action and what not to get approved and he will be required to have so many man hours on the project and with assistance from other scouts.