Just so everyone knows, Better World Generation mod already does this. You can get rid of all world types and just add desert or just plains or just swamp or only have your 2 favorite biomes or your top 3 biomes or 4 or 5 and also adds more biomes like savanna and is compatible with Extra biomes extra large, and biomes o plenty so if you only want one of the biomes from one of those mods you can just have your favorite biome. My favorite combo is plains and forest. and desert and savanna is good too.
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