Biospheres modulators can build planets up to least class 60 (tested) by building a bio.mod. decommission it and build a new one, adding 3 to class of planet each time.

On one hand i can see the altarians and drath with building paradise worlds with enough industry - it is very good-ish and very 'magical', but is it meant to push the balance of the game in favor of a good nation or it is just an unforseen effect of the coding?