The original proposal, and al the discussions contributed thus far are very interesting, and would essentially make the game more strategically/tactically fun...if it can be used effectively by all parties.
In single games, except for the lone human player who would undoubtedly take advantage of it (building fort on/near precious resources too far from home, establing blockade line ect..), all the AI would not be intelligent enough to know how to exploit this new rule, and thus rendered unfairly weak from the start...
Unless you add extra python codes to help them (?), the default programming would not allow them to realize this newly improved but complex rule of play...(by current game rule, they would not build any fort, how are they supposed to realize that forts are now much more useful strategically? Certainly not by reading the new rule in an XML file, then make the interpretation, calculation by themselves...)