In your example, you say

If for example Steem needs about 100 good post every day to keep the current viewership and attract more users, the 10 000 other posts of lesser value are not needed and should earn almost nothing.

With people having such diverse interests, it seem more realistic that we need 10,000 good posts every day to keep the current viewership and attract more users.

I know I have had people register on Steemit just to leave me a comment. I know I have content that is unique -- to the whole Internet. For example, you try to find somebody else that actually shows you how to find, identify, and prepare a wild Insidious Gomphodius mushroom. Or that forages and prepares Fomitopsis Tea, Roasted Chanterelles, Deep-fried Elfin Saddles, with Candied Witches Butter and Cats Tongues -- all on one plate! I've shown people how I find and prepare 16 different wild mushrooms, over 40 weeds and wild plants, over 20 trees, and more than a dozen shrubs and vines. Sure, the audience for that kind of thing is small. But there's no place else where that's happening. I've built up a portfolio of unique content that simple isn't available anywhere else except on Steemit.

When I was curating for the @foraging-trail, there was an active community of foragers here on Steemit. It brought people into Steemit and kept people focused and active, because it was a unique international community, with diverse food traditions. Unique and tight communities that are providing value to each other will grow Steemit and keep it healthy in the long run. I'll be ramping up some foraging community-building projects in the new year.

Without Steemit rewards, I wouldn't be putting that content here. No question. In the early days of Steemit, I had an interesting discussion with @timcliff about how to handle under-valued posts. It led me to carve out some of my posts right before their editing period closed. If only the top 100 posts are considered valuable, removing unique content within 7 days seems a reasonable option.

I'll definitely think more about how I would answer all your questions. They are food for thought, for sure!