I guess I have one more question, which is made moot by another question.
Question 1: Do siege weapons have the same '-1D for every 100 yards' penalty? If so, ignore #2.
Question 2: Imagine the following scene, if you will. Kingdom A starts out on the shoreline, and decides to invest in four scorpions. They have some veteran engineers, so it's not too difficult to give orders to them. I pose that it's now impossible for most fleets to be able to invade this kingdom. The reason?
Suppose we have a fleet of ten units of warships. They're coming to invade Kingdom A. At 500 yards out, A fires a warning shot since, well, it's a fleet of 50 ships coming at them, odds are it isn't a peaceful trade fleet. Combat begins. We have ten units of warships at 501 yards, and they have a commander with, say, a 5 Warfare. Kingdom A has a commander with a Warfare of 4. The seige weapons can't do much since they're out of range, so they sit. Five units move forward, reaching the 440 yard mark. Kingdom A's ground troops shift nervously. Next turn, two scorpions fire. Assuming the engineers can roll even just barely below average, they can hit the ships, since no formation keeps you safe from siege weapons. And even rolling just below average, there's two degrees of success, meaning your warship's now disorganized. Oh, and with another below average shot, so's the one next to it.
It takes 10 turns for a ship to cross 500 yards. With four scorpions, you can, statistically speaking, assume you can destroy at least one-two ships every two turns. It doesn't seem at all possible for those ships to reach the coast and drop off any troops, unless I'm missing something or Kingdom A has some seriously bad die rolls in a row. Am I? Is the armor penetration of scorpions not supposed to work against ships? It just seems that either scorpions are horribly broken, or warships are almost useless in an actual fight unless they only fight other warships, but not against siege weapons (after all, why wouldn't you use scorpions instead of catapults?).