But in a long run some kind of "reputation" in an anon way is needed

Or just make it matter less who the witnesses are. All that is really needed is to pack transactions and sign blocks (this is problematic right now because there is no incentive to actually include transactions in blocks). Voting on hard forks can be modified to work on the basis of direct stake voting, or in a manner better suited to anon witnesses (for example, witness can only change vote once per day, which means stakeholders can vote for a witness without needing to trust the witness to vote in a certain way).

The price feed is potentially problematic. I don't think that is really solvable without reputation.