Incentivizing secondary attacks House Rule

[phayman53]

I was wondering what a good rule would be to incentivize secondary attacks in combat. What I mean by this is that it is almost always sub-optimal to attack with an off-hand weapon, a shield bash, or a pommel strike in GURPS combat. In the case of off-hand weapons, the only time it really makes sense is with a Dual Weapon Attack where both weapons attack at the same time. There is no bonus for alternating weapons in a rapid strike (or in one-two punch combos) as opposed to simply attacking with the best weapon twice. Same goes for shield bashes, with the exception of weapon breakage chances for parrying the weight of a shield and shield slams. Pommel strikes, especially with two-handed swords, likewise only find their niche in close combat--which is not trivial, but is not how they were often used.

In real combat a secondary weapon such as an off-hand dagger or shield (or using those as the primary attack and following-up with the main weapon) or a follow-up attack with a different part of a weapon such as a pommel or butt of a staff/spear/etc is an effective way to make an attack that is more difficult to defend against. In GURPS, however, there is no bonus for doing this and, since the secondary weapon/part of weapon often does less damage, there is often no reason to do it.

I was thinking of making a house rule something like this:

Secondary Weapon Follow-up Attacks:
If an attack is successfully defended against than the next attack made by the attacker against the same target with a different weapon or different end of the same weapon*, all active defenses against the second attack are at an additional -1. This stacks with any RAW penalties for multiple uses of an active defenses in the same turn. This benefit only applies to secondary attacks made on the same turn or the next turn after the initial attack, and only if the first attack was successfully defended against.

*This means a thrust from a spear can benefit from a follow-up butt strike, or a sword attack can benefit from a pommel strike, but a cut from a sword will not benefit from a follow-up stab (same end of the weapon) or a axe attack from a halberd will not benefit from a follow-up with the pick or top spear point (again, same end). GM word is final on whether the follow-up attack is significantly different enough to be harder to defend against.

With this rule, a Dual Weapon Attack Technique on the same target is still useful because both attacks are at -1 to defend against instead of only the second one. Likewise, a rapid strike with alternating weapons gets a slight bonus over rapid striking with the same weapon because the other weapon is a little harder to defend against (I also think rapid striking with multiple weapons should be easier to do than doing it with one weapon, maybe -3/-3 instead of -6/-6, but that is another discussion).

Thoughts?