I think the real problem these things need to solve is proof of time. The big issue with digital currency is double-spending. To get around that the first spend

I think the real problem these things need to solve is proof of time. The big issue with digital currency is double-spending. To get around that the first spend is generally considered the real one, but proof or work, stake, or other are used to indirectly time stamp a transaction. Bitcoin isnt a distributed ledger, it's a distributed notary. Everything (not just currency) will change when (if) a verifiable time stamp becomes available.