How come the Rebel Aes Sedai do not use their far superior knowledge of the power to spy, steal, kidnap, even take the tower? Is there any excuse of that?

 

They have:

- traveling

- can invert there weaves

- can hide their ability to channel

 

and much more, I suppose - but only with those three they can do whatever they wish to. Most of the things even repeatedly.

 

Taking Elaida, Taking the ter'angreal/angreal stash, Spy on anything they wish, Contact the ferrets, Use them for whatever they want to, Go in and take any amount of sisters prisoner.

They wanted to try and avoid open conflict because that would result in sisters killing sisters or at the least, fighting sisters. Even after the Seanchan raid, Egwene was reluctant to invade.

Wouldn't their Oaths make it impossible for sisters fighting sisters (except for the Black Ajah)?