We are considering such limited buy/sell offers; however, we haven't decided yet if they're really worth it.
In Barca we want to set up an automated food distribution internally but require that all outsiders buy/sell from the capital. There is no way of automating this to my knowldge. Here is what i mean (taken from an in game message):
"""
One possibility is to have each region lord set a standing sell order and have Rettleville send our caravans after each harvest to collect the food. On the plus side the system would be very streamlined and require little management once in place. On the down side it is possible for other realms to buy out the food from our regions before he caravans from Barca get there.
Another option is for each region to automatically send a caravan with all excess food to Rettleville while I establish a standing buy offer. Once again this would be very manageable but there is the possibility of traders selling me food I do not want resulting in the loss of much needed gold.
Yet another option is for each region to automatically send our caravans each harvest with instructions to give all excess food to Rettleville. This would be very manageable for the region lords and would ensure that no food is bought or sold by outsiders unexpectedness. Unfortunately this would require me to manually pay each senator for their contributions.
"""
