The impact from organic voting. I'm calling this "vote amplification". If nobody else votes for the post, the vote amplification is 1. If external votes double the post's value, the vote amplification is 2. And so on.
A complicating factor for your strategy is that there's not an infinite pool of organic voting to capture, so treating it as an independent linear variable is probably not realistic. I don't know if there's an easy way to measure the size of the organic voting pool, but you could at least put a ceiling on it by subtracting off the known delegation bots, known self-voters, and the steemit curator accounts.
I'm not sure if it's necessary to track different account types like that. Voting behaviors can always change and delegations can always be shifted. But I think what you're getting at is that it's a lot easier to amplify a small post than a large one.
For example, it's easier to double a $1 post than it is to double a $100 post - and it's basically impossible to 10x a $1000 post (at today's prices). At some point, the account just becomes too large to get much benefit from organic voting.
I also thought of this, but left it out of the analysis because I haven't really thought it through yet. My first impression is that it's an argument for decentralization and competition. For example, there could be moderate sized Thoth accounts posting in English, Spanish, German, Ukrainian, etc... there could also be Thoth accounts that specialize in topic areas: science, history, current events, etc... (one of my favorite features of the test account has turned out to be the English language summary of non-English articles)
So the fundamental thing is probably that there would be diminishing returns as the account grows. And I agree that this mechanism needs to be better understood. This is on the to-do list. ;-)
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