[1.20.4] Custom dimension copy of the overworld with extra custom biomes

[chxr]

I need help understanding if this is possible. As i understand it, modifying the actual overworld is harder and requires 3rd party plugins or using mixins to inject the new biomes, but im not looking for that.

I need to make a new dimension that is a copy of the overworld - but with some other custom biomes.

I've tried making a copy of the 30k biome list of the regular overworld with my own biomes patched after. It does make my biome spawn, but it does it high up in the air, far away from the actual terrain so no actual physical terrain is ever affected by it. I ignore if this is due to the parameters i give to the biomes and / or if there is an easier way to do it or if im doing it correctly or if its possible overall. I've tried using the overworld template and injecting the rest of biomes via terrablender, but didn't get anything neither. Any tips?

 

EDIT: I was thinking to make a customc lass extending whatever the game uses to generate biomes, but I still understand shit about the world generation code (Hell, i think i understand x10 times better the underlaying mathematical implementation at this point) I understand MultiNoiseBiomeSource and OverworldBiomeBuilder play a part in this (NoiseBasedChunkGenerator  and NoiseGenerationSettings too) but on my mother I im failing to understand what can i change to make it, if its even possible.

Edited May 3 by chxr

[chxr]

Now it gets stuck at "Preparing start region for dimension overworld" once i was able to generate a full customzied json. Any insights?

[chxr]

Ok so: Two things to note: It got stuck due to my dimension type. It was previously the same as the overworld dimension tpye but after changing it , it didn't freeze during spawn generation.

ALSO, APPARENTLY, the way I'm doing things, the game can't have two extremely-rich dimensions or it will make the new chunk generation be veeery VEEERY slow. I'm doing the dimension file genreation all in the data generation step now, so it's all good. Mostly. If anybody has any tips regarding how can i more efficently generate a biome-rich dimension, im all ears.