I think ideas like this will run into a lot more problems when we fully realize some of the new front ends of the Steem blockchain. We can't expect the definition of a good curator to be the same on Steemit, Zappl, Steepshot, and ChainBB.
Early communities would also receive an inherent first mover advantage similar to what whales have (although of course with much better equality post HF19!) If a million person strong Justin Bieber fan club subreddit makes the jump to Steemit, they'd potentially be instantly dominating the rewards pool and curation profitability. Imagine the trending page then! Biebs scrolling for hours...
I'm fairly happy with the organic diversification that's been occurring into different topics and areas under the current SP weighted system, and I think it'll continue with the advent of communities.