Therefore Egwene should not have overlooked whatever Tower Law says about the raising of an AS and made Nynaeve one by decree.

She got away with this the same way Elaida got away with demoting Shemerin to Accepted. Shemerin didn't challenge Elaida, and her Hall did not. The same way, if for completely different reasons, Egwene's Hall didn't wish to challenge her decree, as it would have completely destroyed what they were trying to accomplish that night by raising an Amyrlin, nor could it be shown publicly that they didn't have control over Egwene, as most AS would have expected them to have.

That, and not any legal point, was why Egwene's decree wasn't challenged, and why it took some time before the Sitters openly showed their despise of that decree.

Egwene now is fully aware of the awkwardness of the situation, and there is the precedent of Elaida's unilateral action with Shemerin to take into account. Egwene could have put her foot down and insisted that her decree, made impulsively when she knew nothing and felt cornered and manipulated, stood, and the new Hall was now in a position to challenge her over this, and to bring up Elaida demoting an AS and Egwene's vocal opposition to this, or she could negotiate something with the Hall about Nynaeve and Elayne, which is apparently exactly what Egwene did. Insisting that her decree stood as is was no gift to Nynaeve/Elayne: for decades or more they would always have been seen as not properly raised.

The Sitters and Sheriam and co knew better, when they rather chose to acknowledge Theodrin and Faolain were ready for the testing by giving them special permissions and all, but didn't even pretended they were raising them now, when the proper ceremonies and provisions could not be met. Egwene was just a bleary eyed Accepted raised Amyrlin, and she made a very bad call that first night, one that did Nynaeve/Elayne and the other two no favour.

I frankly don't see your point about the Three Oaths. Elayne and Nynaeve were expected to abide by them already and until they could be made to swear them on the Oath Rod. The whole concept of bound Oaths make those no Oaths at all, but that's another issue altogether. As of now, AS are required to swear on the Binder, and until Tower Law is changed about this, this applies to all sisters, no matter how they were raised.

The biggest problem about the Oaths is all the PR fuss the Tower has made about them for millenia, made worse by the stupid habit of the sisters to go around the first Oath on a regular basis and getting themselves a reputation as devious liars and manipulators, which negate the PR effect the first Oath was supposed to have!

Whatever Egwene might have wanted (before she changed her mind anyway), she could not get rid of the three Oaths, unless secretely. The blow, if the WT announced the sisters were no longer bound by the 3 Oaths and only respected them by choice and without coercion, would be devasting outside the Tower. Aes Sedai are barely trusted by many rulers and people as it is, they're in no position to announce the end of the 3 Oaths.

Give them decades or more serving the people and abandonning most of their political games and rebuilding for channellers a good reputation, and maybe then the fate of the 3 Oaths could be discussed again.