OK this post is dead but I voted anyway.
(1). I think the attacker should be able to tell his troops to put a castle under siege for so many round but he has to supply food to his troops just like if they where in town.
(2).Its unfair for the defender to have to give up his gold to an army that did not breach his walls. gold should be in a safe some where in the city not falling out of the sky at attackers.
(3).If the defender is getting support the supporters should battle through a siege line both side's taking losses but if attackers win they should get the loot.
(4).warehouses are in the game for a reason but 4 people with maxed privateering could wipe some one out the defender might as well opened his gate.
(5). so in conclusion every thing is evened out attacker's don't get the city if they win but they still get plunder. defenders can get assistance from ally's when ever he wants. even though his gates are closed he still looses