By "perfect hash function" I mean a hash function which is:

1. Can be done only by a human.
2. Can be done in predictable time.
3. Can be verified instantly by computer.

For example, it can be thought as a CryptoNight variant, not vulnerable to botnets.

If such a Proof of Work function applied to Bitcoin:
Will mining pools disappear? Will decentralization increase? Will network survive when amount of active miners will be millions?