I'd like to see the whole logistics element expanded- I've seen some references to this but I'm not sure how it works yet- what I'm wondering is will it be possible to restrict army stack movement away from supply lines? You could consider a conquered city as a supply dump and limit the radius of movement points or limit the number of turns an army can spend in the field. I know that there are some traits coming that apply to logistics but I'm not sure if that'll actually prevent an army from moving past its lines of supply. If it's not possible to limit an army's movement, then how about a 'Living off the Land' trait that increases unrest or increases the chance of a rebel spawn?