Guild Wars 2

Even with the new changes, stacking sigils will still create massive problems.
First off, you can put a stacking sigil into an underwater weapon and still maintain the stacks, when taking off your stacking weapon on land.
Secondly, you will lose all your stacks, if you have to swap in another weapon for some utility/speed buffs/clearing siege from walls and this weapon happens to not have a sigil.
Lastly, Engis and Eles, will probably still feel the impact of this change harder than other professions due to not having weapon swap.

Now, here is an interesting idea:
The sigils will only provide a bonus, if equipped.
Sigils can be interchanged and are compatible to eachother, so once you are stacked to 25, you can have a +power stacking sigil on one weapon set and a +precision sigil on another weapon set and when swapping, you will receive the respective bonus. You can also have both a +precision sigil and a +power sigil on the same weapon set and receive both bonuses.(however, you can’t have 2 identical sigils on the same weapon set)

If you take off the weapon completely, you still keep your 25 stacks, they just won’t have any effect. Once you equip and select your weapon again, it will provide the respective bonus again.

How it works:
Whenever you kill a foe with a sigil equipped, you will receive a “kill charge”.
This kill charge does nothing on its own. It will merely determine, how many attributes you get from stacking sigils. If you have, says, a weapon with a sigil of life on it, you will receive an amount of healing power proportionate to the number of stacks. If you swap to another weapon set with, says, a sigil of bloodlust, you will now receive an amount of power proportionate to the number of stacks.

Now, of course, this is a huge step down from the current system, but remember, that numbers can be changed. I like the concept better than what currently exists and definitely better than the half-baked concept, which is about to come. Obviously, those sigils would need a slightly stronger attribute bonus to still be worth being picked over other alternatives, but at the same time, you’d no longer be restricted to one kind of stacking sigil or could even do crazy stuff like focusing on different attributes with different weapon sets to a much larger degree, than you can now.

Another idea and the one I would like to see implemented is a slot for stacking sigils and a way to unlock them for the character to choose what sigil they want to use for which build, that way instead of having to invest in multiple weapons just to house these sigils they can invest in sigils to make their build more fun to play and every class would have the access to being able to build and carry stacks on to the battlefield.

This idea has its own pros and cons. On one hand, it offers greater customization. You could have, as you point out, different stacking sigils on different weapon sets that better cater to whatever role that weapon set fills. On the other hand, should you want the same stat stack on different weapon sets, you would potentially need multiples of the same sigil.

While Klocknov’s idea addresses this, I’m not in favor of his solution. When picking sigils, we as players should be forced to make tough choices in selecting those that best suit our professions and builds. Stacking sigils are no exception. We’re not entitled to the benefit of these stacks, but that’s what a stacking sigil slot independent of weapons would make us.

Anyway, it’s an interesting idea, naphack. I’m not against it, but I don’t think it’s what ANet wants for sigils.