Has anyone thought of changing emeralds? 

They've always seemed like a bit of a throwaway resource unless you're actively under siege (a pretty niche occurrence) and are almost always just used for approval bonuses. I'm not very familiar with modding or how difficult it might be to edit the emerald booster effects but something like "+1 resource on strategic/ luxury resource extractor" or " -20% cost on marketplace trades" would be a much more interesting effect (in my opinion). 

Just a couple ideas, keen to hear you you all think!