BOA does a wonderful job of modeling attrition from movement and lack of supply. Once inside a city, however, particularly one with a Depot, an army of virtually any size can safely hole up for the winter.
One feature of Forge of Freedom that I especially like is that armies during fall and winter months are at risk for disease, which can spread within an army. Thus, a large army sitting together in one spot is especially vulnerable, particularly during the winter. This feature encourages the realistic dispersion of forces into winter quarters instead of leaving them in perpetual uber-stacks in forward positions. Which, in turn, makes winter warfare doubly difficult. Which, in turn, makes the overall pace of the game more realistic.
Any chance of AACW having a similar feature?