So if there are many such systems, maybe each one could be like its own top level domain: your system is the .com, another system is the .org, etc. Although of course we’d have to wonder: how big is the space of all such systems? With just one or two variations (expiration date? PoW required for initial registration? Method to transfer?) the space could explode pretty quickly to be pretty big. So who keeps track of the list of actively-used systems? (Maybe we would need a Decentralized List!)