Are you saying that an algorithm that cannot be simplified cannot exist?
I'd be happy with good approximation of double SHA-2 
Even if you find that a (SHA-256)^2 function can be implemented with depth=2 and width=1,000,000,000 - it would be useful work that could be built upon.
Quite unrealistic, but if done - SAT-solvers will step in.Hehe. I like encouraging people to explore this. Good learning "exorcize" (pun). 32 bit addition logic for botnet: http://jlcooke.ca/btc/sha256_logred.html
Just do that about 768 times and reduce!
