[Puke]

This is already being done (to some extent) in the Imperialism mod. Which i need to run turns for, but since ive been trapped at work for such stupid hours over the Last few weeks...

anyway, i did the exact thing you describe - but only for political savvy. high cost to raise or lower a few points, lower cost to raise or lower beyond the threshold. and it pays off even with fewer players (works better with more players) because its more profitable to subjugate AI races (with a high bonus) than it is to conquer them outright.