So I was reading THIS post
http://www.invirtuo.cc/se4/viewtopic.php?t=2998
about 'core' mining facilities, and was relating them to the borehole miners in SMAC, and got an idea.
Since value improvement plants stack and can take negative values, maybe condition modifiers stack the same way? We could mod a massive planetary core tapping mining facility that would steadily worsen the conditions of the planet. A planet full of such facilities would soon hit the lowest condition possible, which i think will even start to cause negative population growth.
You would have to ship people in from other parts of the empire to work on your hellish mining planet! isnt it great?
well, if it works.