Well, Toady set himself up for a tough slog in trying to make combat resolution so physics defined. A little abstraction can go a looong way.
The big problem right now sounds like swing speed is fixed, which makes mass the dominant factor for impact calculation. Also pretty unrealistic. Swing speed is, at its simplest, a function of (strength / mass), which if you just translate back to (velocity*mass = impact) means you basically end up at (strength = impact), and lighter weapons are swinging a lot faster, meaning they should be harder to avoid, and thus better overall. Obviously not very realistic, but it is more realistic than (mass = impact)!
Now, real life calculations against armor quickly get absurdly complex. Rigidity, absorption, depth, ablation. yada yada yada. Now a lot of these values are fairly fixed in any contest between Weapon A and Armor X - but the variables that change most on a swing to swing basis are usually Thickness and Deflection Angle.
First off, no suit of armor is uniformly thick. Design and Weight considerations demand that there be gaps, overlaps, and different thicknesses of armor in various sections. Helms tended to be the thickest and are often well rounded or angled for deflection (but require gaps for sight and breathing), Breastplates tend to be fairly thick, but are often flatter and difficult to design for deflection without adding a lot of weight. Legs and arms tend to be thinner in general, but a skilled wearer may be able to quickly angle them for excellent deflection. Etc.
Assuming a warrior could repeatedly deliver a series of blows of similar strength, the results against a given suit of armor would be primarily decided by the exact location and deflection angle of a given stroke. Many strikes would bounce off harmlessly against good plate mail, causing no injury or ablation whatsoever, a few might cause minor cuts or bruising with the bulk of the blow stopped or deflected, whereas a single lucky or well placed strike might still immediately kill or dismember the wearer.
Ablation was not generally a major component of ancient armors. They could be damaged and their efficiency reduced certainly, but more often than not an injurious stroke was simply delivered through an existing gap or via a well delivered crushing/piercing blow, rather than a rain of consecutive attacks intended to gradually degrade the armor. Piercing weapons would tend to deliver slightly injurious hits every time, killing through cumulative wounds rather than meaningfully degrading the armor. Only blunt weapons would be likely to have a useful ablative effect on rigid armor. Conversely, blunt weapons would repeatedly injure when used against non-rigid armor, such as chain w/padding, but would cause very little damage to the armor itself.
My real point is that all of this would be REMARKABLY difficult to model via physics, even for so ambitious a game as DF. Abstracting the combat system to a moderate set of strike locations, angles and piercing/cutting/crushing values would produce a set of remarkably detailed and realistic looking results without the overwhelmingly difficult to resolve set of mathematics that it looks like it is setting out to solve.
But it will be interesting to see how it goes. It is technically solvable, but it could take a very long time.
On the flip side, the interface is now a good 60% more obtuse than it was before, which I didn't really think was possible. Burrows are still giving me fits. Especially that one keystroke deletion terror... ;P