i just ignored workshops, lumbermills, windmills, and watermills heh
i like the resource based improvements since theyre less stale since they have a chance to find stuff which is fun. i made them buildable without resources to make it so all resources could be found eventually if you're lucky, and balanced them against the other resource improvements.
the mills and workshops become better with certain techs, and i haven't put much thought into how they could be made more fun. i doubt ill do so before shadow comes out, but later on ill consider something for them.