As you've eluded to, trying to forecast wind damage gets pretty complex when you also take foliage and "soil condition" into account, as we found in central FL (2004). A great amount of the wind damage occurred due to fallen trees and weakened ground and root systems. Whatever survived Charley was weakened and more prone to damage, or to cause damage to structures. The entire landscape gets changed across an area hit by a major hurricane, and this likely increases the potential for damage in the future. Likewise, as many experts have pointed out, development along the coastal areas has vastly increased the $$ potential for devastating wind damage due to tropical cyclones.

I think we're doing pretty good just to be able to estimate the features and characteristics of a hurricane! Trying to come up with a standard correlation to the extent of wind damage in any given area is nearly impossible.