I know this sounds probably a bit iffy to some people but how about the option of using Iron to make tools. 1 iron ingot = 5 tools or similar. This would allow higher level players who don't necessarily have as much use for recruits (though a meat shield is always useful I suppose) to produce the massively high level of tools required at a faster albeit more expensive rate.
Another useful trait of this is lower level players (pre level 30) would probably find the ability to sell Bronze Swords to the higher ups a good way of earning the gold coin they need to build their own towns up.