Isn't there a router bit that comes close to the shape we want? If you glue a hardwood leading edge to a strip of balsa and then feed the whole thing through a router with this bit, it would come out the other end with a consistent shape. Once it is set up, you could make a new set of blade blanks in 30 seconds.

I have no idea what it costs to make a router bit to suit, if there isn't one already on the market.