The 20% rule is ridiculous.

[Toxcatl]

My point is 20% is too extreme.

I disagree. I'm sorry if it sounds harsh, no offence, but...
You had the whole season, and didn't manage to climb from 840 to 900? It means your association just isn't good enough for Gold 2. Why top divisions should be guaranteed to everyone who plays long enough? It's a competition, not farming.
Fly or die.

How do associations with less than 6 teams even stand a chance?

Do they?
Get the full house, I guess it's not that hard. And good luck next season!