Good luck, this is a great idea.
I make a bunch of different home-made instruments, from stringed to percussion.
I recommend poking around the Cigar Box Nation site. There are thousands of do-it-yourselfers on there and they have made many variations of what you intend to make.
Also, a great book entitled "Hand Made Music Factory" by M. Orr is a wonderful book that shows you step by step how to make a variety of these instruments from reclaimed/recycled materials.
The web has everything you need.
But your idea sounds great, have at it. You can always modify it after you build and the trial by error begins. Bottom line: great idea = just do it!

