I would very happy to see population immigrate from province to province.
currently working on a project lie this, where population that cant feed themselves emmigrate.
If population can migrate through open borders that would be fun.
I beleive this would allow players to take an easier approach, and force warrior players to plan economically before engaging war<
and as an added bonus, it may require two warring parties to settle for peace which is always fun. (IMO)