[kushti]

Some alternatives. Permacoin(http://cs.umd.edu/~amiller/permacoin.pdf) has mostly the same security properties, but effectiveily non-outsorceable, and work done is useful. We made the first open-source implementation of that https://github.com/ScorexProject/Scorex-Lagonaki/tree/master... .

I also have paper draft about better Proof-of-Stake protocol, and would like to share it with people from academias to get a feedback. Please write me ( kushti at protonmail dot ch ). I also have half-written paper draft about PoW+PoS hybrid chain.