There are sturdy light woods out there, I just don't know of any. I'm not very familiar with alot of wood. It seems alot of the lightest popular woods are about 7 or 8 pounds (I forget which) per accordion.
I was gonna prank call a builder and say that I want one made of "Charles wood." However, I don't think they'd find any humor in it though!
Italian makers will beg to differ and claim wood quality does influence tone quality. They are convinced Olive is the loudest wood and I tend to agree after trying one.