Hmm, i'm starting to believe it's just impossible with modding, it's hardcoded.
I have generated a few more dozen of worlds and saw that whatever are the settings i changed, the capitals of every races (not just goblins) can be hugely overpopulated (several thousands) sometime in only a 100 years old small world.
I even tried more added to what i did previously :
- [CRAZED] to every races so they would not ally each other (as i counted then on war to be the population control device there)
-removed all the [TOLERATES_SITE:...] token from an entity that allowed a member of the entity to go live in other race sites, that because i noticed crazed didn't worked during worldgen as goblins, dwarves and humans were stil happily co-existing in the same sites, despite the crazed token should have forced a bloody population number control
-removed all the domestic , pets , cave/good/evil animals from every entities, the goal was to remove all those thousands of animals (unfortunate the trolls had to go too) from capitals overpopulation and hopefully get the population to have more food problem .
unfortunately while there was no more animals overpopulating sites, the populations never took any impact in 100 years , as if animal food shortage has no influence in worldgen.
-lowered the maxage to 20,50 for every races
And after 100 years of worldgen, still no go, i saw enough forest retreat with 3000 elves, towns with 2500 humans, dark fortress with 2000+ goblins generated in the several dozen of worldgen i did.
As if i didn't changed any settings and used the default raws only :/
Even people dying young (as the maxage is very low in comparison to default) does not limit populations, i'm wondering if the very bad respawn bug reported
here that happens at gameplay time is happening at worldgen time too.
Because i can't see why things get overpopulated in only 100 years in the exact same way as when (in default raws) those populations could all live more than 100 years (and some immortals like default elves or goblins)