Instead of trying to make a coin 'cpu only', how about a coin that would allow blocks generated from SHA256, Scrypt or CPU? Difficulty adjustments would depend on the algorithm used and would be adjusted to seek parity. The advantage would be that the network would be supported by a variety of hardware making it the most secure and would pique the interest of any miner regardless of their hardware investment. With an open model algorithms could be added as crypt-currencies evolve.

Not sure if it is even technically possible, but thought I would throw it out there....