After I posted the link to my thoughts on spending HP (and thus depleting a reserve of grit and skill) to do more damage to your foe (depleting his reserve of grit and skill) the poster Kalzazz made a comment, which had an interesting bit in it:
‘The enemy made his attack by 3, I need to make my parry by 3 to have a shot. He seems to be a normalish human looking guy swinging a broadsword, and I don’t think hes a weapon master or he would be throwing multiple shots or have a higher margin on his attack . . . . I am wearing light plate with fortify 1 . . . do I take the hit, or do I burn an HP to try and parry?’
Hrm, I say.
The concept of trading margin of success of an attack directly for difficulty in making the damage roll isn’t how GURPS works, generally. When attacking, you make the risks ahead of time. I will attack for the face (-5) or the left leg (-2), and I’ll make my attack harder to defend against – a Deceptive Attack for -6 to hit in exchange for -3 to defend. So for the face punch at -3 to defend, I have to absorb -11 to hit. That probably means my skill is something huge, like 25, or I’m using one or more options, such as All-Out Attack, to boost my skill.
Having margin drive difficulty of defending tends to remove the incentive for targeting more-difficult areas (that same basic philosophy holds for when margin results in damage).
But what if that margin could mean something? I’m not sure I’d do this in vanilla GURPS, but if I were using Action Points, I might have post-attack margin impact defenses, but at a lower ratio than deceptive attack.
So if -2 to hit gives -1 to defense when risked ahead of time, for every 3 or 4 full points of margin on an attack, the foe is -1 to defend.
But . . . you can spend APto bring your defenses back up to normal. It’s not as draining (nor should it be!) as Feverish Defense, which is 1 Fatigue Point to get you +2 to a single active defense roll (and suggests 5 AP per +1 to your defense roll in general). At a 3:1 post-success tally, making an attack by 0-2 gives no extra benefit, 3-5 is -1 to defend 6-8 is -2, 9-11 is -3 (and making a roll by 10 often has other benefits). At some point you’ve probably rolled a 3-4 (at Skill-14 or lower) and have rolled a critical anyway. Perhaps it caps out, then – sort of a rule of 16 thing – so random luck can’t bless you with more than -3 to defend.
But that can be countered by spending an extra 3 AP. A few of those in a row, though, and you’re tired. Or using All-Out Defense to reap the benefit of the 2 free AP that maneuver gets you for such defensive moves.
I’d have to play it to see if it’s more trouble than it’s worth (it might be). You’d have to really look at the AP economy as vital to fun and pacing.
I also sort of like the concept of spending as many AP as you like (but no more than 1 FP at a time, though you could get close) at a ratio of 5 AP per +1 to defend as a scaling version of Feverish Defense.
Anyway, Kalzazz took my D&D and thought about GURPS a bit, and I think there’s something there.