Well really, the pertinent question is whether both attacks receive full force when making two attacks at once- if you're using a pair of adamantine blades you don't need to put a huge force behind your attack to do serious damage, whereas if you're using crappier weapons it almost certainly won't be worth it (barring freakish skill / the concept of feinting is implemented.)
The more pertinent question is whether or not Toady is working towards building a full system of understanding combat, so that all individual actions are understandable within the same framework, or just adding random things without any relation to one another.
D&D-style dual-wielding, where two weapons means twice as many attacks with just some -2 penalty to damage is completely contrary to the sort of combat he's been otherwise trying to work towards.
There is a reason that there was essentially only a couple dual-wielding weapon fighting school that ever sprung up, and it sprung up for formalized duals amongst people not wearing armor, and where, even then, the off-hand weapon was made for defense, not offense. Against armor, an off-hand weapon is useless, and a shield is much better protection.
Likewise, jumping attacks (which are already being talked about) are not taught in any martial school for the simple, obvious reason that you lose your balance quite easily attacking while mid-air, and you never want to be lying prone in melee.
Barring something like jumping up to swat at a bat or some other very small creature, attacking an armored, balanced opponent with their feet planted in a jump attack is just going to wind up with you bouncing off them or them swatting you aside because you'll have no leverage. This
needs to be reflected in the game's mechanics.
And the problem is, it seems like Toady doesn't seem to know it:
I don't have much to say about multiple attacks or how penalties for that would work. It's pretty complicated in the end. Certain things would be easy and effective (say, if you had needles you wanted to poison people with, or light sabers or something), and certain things would be wantonly silly, like a punch+kick maybe. I haven't really addressed this in any satisfactory way, and I'll probably be walking a fairly idiotic line until I actually focus in on combat a bit.