In his recent critique of cryptocurrency/blockchain systems, David Rosenthal cites a study on crypto "decentralization" which claims a Byzantine Quorum of size >= 20 would provide a more robust "decentralized" solution than Bitcoin or Ethereum (https://arxiv.org/pdf/1801.03998.pdf). Are there any existing services that offer something akin to what he describes? If not that particular design, are there other alternatives worth looking into?