Weapons are out, but what about armour? How about cuendillar shields, helmets and chainmail? Even if you made it extremely light it would still be unbreakable.

They could make armour, cuendillar or otherwise. However, it's debatable if 1) such armour would be very useful - the lack of flexibility and hence, the need for a perfect fit might make it difficult to use 2) they certainly couldn't make it in sufficient quantity to protect a significant number of warders. The CoT descriptions make it clear that most AS are barely capable of churning out C'dillar.

They could just turn existing armor to cuendillar for the people who will be doing the heaviest fighting. I think cuendillar is noted for being light AND strong; I think it would improve mobility if anything. Keep in mind that not every section of armor need be made from cuendillar in order for it to make a huge difference; only the vitals need be protected (helmets, shields, breastplates). And not even the entire object need be made from cuendillar. We see that with the chains in Tar Valon. So enough mobility could be left.

 

Of course, this would be hard anyway considering it isn't necessarily easy to do. Still, a few hundred sets for the warders/aes sedai shouldn't be too hard.

 

 

As far as creating a weapon to be used against shadowspawn, I see no reason why the oath couldn't be twisted in such a manner. To me that's the same as the oath about lying. I don't see why they would be able to twist one and not the other.

 

Besides, we see the other oath ("last defense of my life" or whatever) being "twisted" by Aes Sedai frequently as well. Recall Dumais Wells where they ran into battle so they would feel endangered, or Mat's battle near the end of KoD where they felt (I don't have the exact wording) "reasonably afraid" or whatever. The Oaths really depend on the Aes Sedai's perspective on the situation. So, why couldn't they make something in order to kill Shadowspawn?