What about the following idea (don't know if it's modable that far):
- set base approvol far down
- give all major civilisation one super approval-bonus project from the beginning on their homeworld to compensate the low default approval
- Arakis shouldn't get approval bonus, so the resistance (Fremen) is fighting their guerilla war (-> random events on arakis, frequency depends on actual approval)
- Arakis should have high economy bonus (Spice!)
- Victory condition could be to get Arakis to a certain approval, which only would be possible by conquering all the Super Approval Projects out there. This means conquering Arakis would give you a huge economy bonus, but to get rid of guerilla events and win the game, you have to conquer at least all other homeworlds.