How is that different than an online database of every possible configuration of random numbers? What use could it possibly have?
If you are thinking along the lines of restoring data from a SHA-256 hash. I have bad news for you. It won't work.
Instead of mining a fiat currency, people could mine for knowledge.
Is this not the kind of idea that crypto has been waiting for?
How hard would this be to dumb down for mass adoption?
The library of babel as you described it is not encrypted, so there is nothing to decrypt, and I don't see any way to get knowledge of collections of random letters. Random, by definition, contains no information.