introducing reputation
How novel, somebody should do that.
Bitshares did it in an extremely poorly designed way by having an IPO where it's possible for the dev to to create thousands of mule accounts, send BTC in with all of them, get infinite premine + all his money back, then have plutocratic voting to determine delegates based on who owns the most coins afterwards. The entire thing is a train wreck. You can't get rid of mining for distribution, amongst numerous other changes they would have to do for how their system works to make it not a blatant scam.
I publicly (on this forum) warned bytemaster about that while he was designing it. I stopped following his work last year. He did present at least one good idea I adopted as optimumselect the block solution with the lowest value over some interval to mitigate the orphan issue.