Like I know this has been reiterated with BOINCcoin but I mean like you mine bitcoin, and its not spent trying to decrypt a sha256 hash sum, but rather fold proteins and what not. I mean an easy work around would be to fork primecoin to sha256 (if possible), and then bitcoin would be supporting the primecoin blockchain AND finding prime numbers.
Not possible. That would be like trying to find the sum of 23 and 17 as well as finding pi.
SHA256 ASICs can do one thing and one thing only, hash SHA256.
ASIC stands for Application Specific Integrated Circuit.