I still fail to see what this whole excercise will gain us. In numbers, it's ridiculous - with equipment, morale, cohesion and training you have four values there, so splitting up training affects 1/4th of the CS, and adding a terrain bonus 1/5th. That means in the best case, you need a 40% terrain effect difference for a 10% CS difference. So in most of the cases, it wouldn't even matter.
That is why I wanted to make it more like efficiency. Make the total efficiency (at 50% efficiency, your CS in a particular region type will be reduced to 50%) to be 300%. When you first recruit new units, your units will have 100% efficiency for three categories (rural+badland, siege, mountain+woodland). But once you start training your men for higher rural+badland efficiency, the other two categories will go down and will become something like:
rural: 150%
siege: 75%
mountain: 75%
What this will do is when you have an army coming for your city trained for 'siege' type, you can smash them by actually leaving your fortification and fighting them outside of your city in a region where your army can gain higher efficiency.
Edit: Now that I think about it agian, I think it is better to let different unit types start off at different efficiency with different cap for different types.
For example,
Infantry - 75% for all types. Max at 150% (Total eff. 225%, if rural is at 150%, other two types will be at 37.5%)
Cav - 125% for rural, 75% for woodland, 50% for siege. rural caps at 175~200%, woodland caps out at 150%, siege caps out at 100%.
Arc - 100% for rural, 75% for wood, 100% for siege. rural caps at 175%, woodland caps 150%, siege caps at 175%
MI - 85% for all types. Max at 175%
SF - 100% for all types. Max at 200%