Board Game Arena

In my imagination, the opponent's ELOs would persist to be the major factor for calculation, while the gap in result could make up 20-25% or so. So it's still desirable to receive more for a victory against 500 than 200 ELO no matter the gap.

And yes, as I pointed out in my texts, you could transfer the experience of having tension not only into close games but all games, because even when it's clear who wins, unlike now, it actually makes a difference how well you perform until the end. That is one main purpose of the topic, besides the alleged (debatable) fairness.

Still winning against weaker opponents will be rewarded somewhat higher than currently. I don't think it is desired.

I also somewhat disagree with a concept of translating points into ELO, it feels a bit artificial and very uncommon for most of the sports. I.e. in football, basketball, volleyball, tennis a win is a win. It can be 45:8 or 78:77 - it is still a single win. It works for everybody, why shouldn't it work for BGA?

This cannot be good for some games, such as Koi-Koi for example.
If, near the end, you have the choice between something that guarantees you a loss by a very small margin, and something that might give you either a win or a crushing defeat, based on random chance ?
With the current ELO system, you should obviously push your luck, in the hope of winning, rather than finishing the game earlier with a guaranteed close loss, even if this gamble might result in a abysmal defeat.
With your suggested changes, this would basically change the strategy, because you might want to play it "safe" and lose only a few elo points, rather than risking having a huge gain or loss of points based on pure luck.