STEEM has the advantage that no witness knew they were "mining REP" for 4 years. So if you implement a better REP system (perhaps taking parameters such as account age) and then convert the current DPOS protocol into a REDPOS one you should get a stronger blockchain.
Wont be perfect, but sure better.
Ouch. I don't mean to be rude by shutting down this trail, but I can't continue. There's too much wrong with your thoughts. No one has ever "mined rep".
Reputation is purely built on who your upvotes are from (or the SP they're allocating toward your posts), and the rep of those who are commenting on your posts (or at least that was a thing way back when).. this is why voting bots were dangerous. You'd get a huge rep bump simply for having a "whale" (or voting bots) with high rep vote one time on your post.
Rep is not the right tools. Trust me. Pick something else...
@blocktrades already explained that the current REP system on STEEM was coded as a "bandaid".
On a REDPOS protocol, as REP would be a significant aspect of the witness rank, I think it's pretty obvious that it should be better coded (a REP system that really works).
However the current REP bandaid would be enough to take out Justin's sock-puppet witnesses and that's why I consider there is real potential for a protocol improvement for a (so called) social blockchain.