By that measure, shooting a gun is holding the handle, pointing it in the right direction and pulling the trigger. Melee combat is just holding a weapon and hitting your enemy. Playing a piano concerto is just hitting all the right notes on the keyboard. I agree that the knowledge of where is vulnerable is bloody obvious. I have always thought that Ambush measured not knowledge, but the ability to lay down a precise attack, probably in poor visibility, probably against a moving target, probably against someone whose armour covers up all the vulnerable points, possibly against someone trying very hard not to be ambushed.
5 years of ancient fencing told me that the hard part of learning is to avoid killing your partner. In fighting, the hard part is not landing a blow, it’s preventing from being hit. What I said was not wild guess, it’s experience. Look at military training: what takes the most time is how to survive, becoming fit for fighting, using material. Not how to kill, that is bloody easy.
Besides, ambush is meant for use on unsuspecting targets. RMSS page 196.
You don’t aim a blow at a foe that is actively defending itself, you hit him were you can and when he is helpless, you finish him off. I positively love fencers that target some areas of my body, I ostensibly leave them unprotected and counterattack while they lose time readying THE blow they want to land.
Armor? Weak points learned in a couple of minutes. Eyes, groin and necks still work admirably. With the right weapon, your don’t even have to aim, just hit very hard on the head or on the neck and laugh like a madman. I mean, if you were given a knife and told to down an unsuspecting guy, how hard would that be?
(And you mix up knowing where to hit and having the skill to do so, skill at arms is managed through weapon skill. But since an unaware foe is not fighting, not even fleeing from you, there should not be any attack roll. Hitting the guy is just like shooting a sitting duck at point blank.
This assumes that all armed ambush has as its goal the quickest possible death. That no one ever wants to take a prisoner or merely put someone out of action. I don't think that's a tenable assumption.
Avoiding to kill someone is far harder than killing, that’s for sure. That’s what the skill subdual is for.
Now, ranged weapons are another matter. To be honest, I don’t think RM handles them well enough but I have absolutely no idea to improve their mechanics without using a new way to resolve attacks.
Ambush should disappear, replaced by a mechanism that would allow for quick and easy dispatch of unaware foes.
Silent kill should disappear, use wrestling instead (basically, you just have to prevent the ennemy from yelling and control his body while it lumps to the ground).
A better control over hit location and critical result, for those who feel it is necessary, should come from weapon skill and nowhere else.
Subdual could be managed or caped by the lores or technicale/trade skills: want to knock out a goblin? Use subdual caped by your skill in first aid (goblins) or goblinoid lore.
Actually, besides hide and silent move, all the skills under the subterfuge group can be replaced by others, from other groups. I have the feeling that they were put there because there was the need to give roguish professions their set of dirt cheap skills (which is not a bad thing, but the end result is redundant skills). In a system without professions, those would just be wiped off the board.