i agree with you that the starvation effect to the garrison is insufficiently represented in the game. IMO the population should suffer a siege, expotenially if it's possible, to represent starvation.

however i had to disagree with the blockade theory as the cities are represented as inland and so it shouldn't be included as part of the siege factor.

it came into play at the siege of athens because the city walls are designed to include the port with the city and so the spartans are unable to cut their food sources.

my 2 cents