A) Hashing an already hashed password does nothing for us. How is an ASIC (that only does hashes) gonna find a twice hashed password?
B) This discussion has already run its course, and been answered. I was corrected 2 posts down:
For cracking, you have the hash of the password. You then take your password guess, hash it, then compare that hash to the value you have. Rinse and repeat several trillion times.
Granted BFL ASICs can't be used to crack password but I'm pretty sure a more complex ASICs could be used for both.
The hash has to be compared a list of wanted password hashes instead of the required difficulty mask.
I wish someone could come-up with an estimate of the difference in gates and bandwidth required for the simplest of dual uses.