He really hates structured activities. The questions really are nuts, hey?
But now I remember we have an old meccano-type set at my parents. Might see if he's interested. He'll probably want to dig the driveway up again and/or work on his gold mine/concrete factory.
My parents bought him a couple of little kiddy model planes which he put together. But then he wanted to use parts from both to make a totally new plane. Unfortunately the slots didn't line up so they weren't compatible.
His enthusiasm and creativity often exceed his ability to actually do stuff, which is a real problem.
Thanks for all the suggestions