I don't think that it would be worth the effort. Many (I guess most) shit accounts have a low rep, so one would need to filter manually and go through all the mess just to find a few interesting posts.

Since the majority of people actually don't want to see most of the downvoted stuff, there is not much money to be made with such a system. It's not a super bad idea, but I think it should be solved within the regular platform by providing more filtering features.

Sustainable platforms can be found where the mainstream hangs around. With currently only ~ 1.4 million users on chain it's probably just a waste of time. Many good projects died, not because they were bad, but because the targeted audience was just too small at that point in time.