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It would get a larger relative curation not a larger curation value. The 19$ bet could still get 5$ curation (around 25% of the bet) but the 1$ bet could get 50 cents (50%)

Well, that's definitely preferable to the extant system, IMHO. At least it supplies a superable reason for curation rewards.

I'm not actually sure that is where we need to aim, TBQH, but it's sure food for thought.