The more and more I think about it; the less and less I like the idea of using specialists to balance improvements. We are going to end up unbalancing specialists, and making them too powerful and common, and not really solve the improvement problem.
If towns give a free specialist, and require social contract, then the ideal strategy would be to avoid towns until close to Social Contract, then spam them on less useful tiles, build them up, and use the specialists. That isn't strategy, it's an exploit.
I'm also discovering how less is more; so instead, my improvement changes are largely a revert to what RoM 2.71 had (the last real version where improvements were balanced). I have removed the Trade Center improvements, as they were a bit superfluous. The factory, workshop chain remains largely unchanged, and the town becomes the producer of commerce again. We don't need to create new features to balance the game, but just look backwards enough to see how we used to do it.