You forget Jordan explained this was impossible. The experienced sul'dam are almost seing the weaves after many years of using an a'dam (and Tuon is good because of her aptitude to lead and to gain obedience and loyalty - and she had one of the best der'sul'dam of the Empire to teach her the ropes... but in the end she can't have been doing this for many years as she is just 20, and she is just a gifted amateur sul'dam who trains damane for fun when she can spare the time from her numerous real duties), but Jordan said they will never channel on their own without a conscious effort to learn how to embrace the source. They don't become sparkers, years using the a'dam or not.

The sul'dam with Elayne did not begin to channel without a conscious effort, no more than those with Mat's Aes Sedai. Elayne's were pestered until they admitted to seing the weaves then broke down and gave in and asked to be trained (well, aftet they stopped asking to be leashed). They still need to be guided (by the Kin or Joline/Edesina) through their early embraces of the Source, the very same way any other learner must be. Only those with the spark who aren't found in time end up embracing the Source inconsciously at some point.

Tuon or any sul'dam embracing the Source out of a loss of control/an accident is an impossibility. Some thought she would channel to save her life or someone else's. Again impossible. That's for sparkers, not learners. Learners have to go through the baby steps. Early on, Tuon would barely be able to embrace the Source reliably each time or to lit a fire, just like Egwene on her own in EOTW.

If Tuon channels in the series, she'll be at early novice level.

But to become a channeller, Tuon would have to be guided and taught, and so far it's hard to see what scenario could possibly play out for her to ask for that. It would take some earth-shattering developments among the Seanchan for their Empress to decide to learn to channel. The story could very well end with Tuon still refusing to have anything to do with her latent ability. It's not Mat who would complain.