I have two quick quesitons, When you put the aluminum sheet metal over the top of the guitar, wont it be hard to bend it to the contours on your mock up drawing. In particular, the upper arm contour seems oddly shaped, not like a normal strats contour that would only require a straigt bend.
Also if you moved the cutaway in question up like 3 or four frets, then made a sort of carve in the wood that replaced the cutaway, would that satisfy both the design and practical problems. I don't really know if it will help out, but i think a thinner bit of wood between your fingers and their destination might make reaching the frets easier.