Sorry, but i fail to see correlation between high mining difficulty and old empty used address. Difficulty isn't affected by what address you use to receive mining reward. Can you elaborate further?
They still need to create valid block, otherwise current full node on that network would reject it.
My thought is that on a closed reduced "fake" network even some old networks could do the job ! ??
The *addresses could serve to create just some fake transactions to just fill the blocks to blur the clues, so to fool future watchers ..!
It looks like i misunderstood your earlier statement. But such addition will add debate such as,
1. It may introduce some centralization.
2. Risk of the private key (used to create authentication signature) got leaked.
Yes, here is the idea.. it is to use the whole structure, with many departments=conditions, to work like a fingerprint to authentificate /sign, ...
do the cryto-keeys could not be implemented
blindly .. using such protocols:
https://en.wikipedia.org/wiki/Blind_signature ??