How about a tag that allows you to build money, science, espionage, or culture, but at an altered hammer rate. It would be great if you could put the hammer rate maybe in a percentage, so at currency you can build gold, but at only 25% of the hammers put in, later techs could allow a great percentage. Going with that idea, how about a tag for civics that alters the way hurry production works, this would work best with hurrying with gold, so you can have an earlier hurry with gold, it would just cost more gold to build, a higher gold to production ratio.