One thing you should consider is that if you are going to have a blockchain implementation then it would be best to separate the "content" from the chain (e.g. just keep the hash of the content in the block that is stored).
In this way any content can be deleted if required as you would not want people using the system to end up in jail due to unwittingly having "illegal content" stored on their computer.
Of course you could just encrypt all stored content but authorities can demand your password so that isn't necessarily the safest approach.