I think you're way ahead of me on this one.  Every time I think I get the wings to fold, I need to go back and adjust the weights and make morphs for them to look good.  The bird wings could almost use joints instead of bones - with the joints, the wings wouldn't deform.  And to move it feather by feather - lots of work.

The bat wing videos look great - did you use morphs on the pair of wings?

Never Give Up!