I agree that more ladders would be nice, but I think that suggestion deserves its own thread.
I also think that added to that suggestion should be that ladders can have more positions on the wall and that ladders should require resources to create (I.e. X amount of wood per ladder) that could then help balance how many ladders were used each time and create sieges with different numbers of ladders from the attacking side. You could then also use a similar resource based system for all siege equipment.
Although again I have no idea how much work these suggestions would require in order to be implemented.