That it would explain things very simply is a good argument that's what they are; I don't think Sanderson any more than RJ is planning to throw large scale and previously unknown elements into the last book. It would be like a fleet of Klingons coming out of warp next to Tatooine in the final minutes of TESB (or AotC, if you prefer). Anyone who's ever written a HS essay knows you don't add a bunch of fresh data in your conclusion.

The two problems I have with it is that the lone Aiel mentioned isn't described with the characteristic moving black pulse, but with dark eyes, and that if they're channelers killing an unarmed merchant refugee with a blade seems odd. For that matter, if that were the case I'd expect the OP to be used razing Kandor, and for Barriga to mention it; people who've witnessed a battle fought with the OP have usually displayed (understandably) strong and vivid memories of it. However, while it seems odd to think people intending to leave no survivors and take no prisoners would masquerade as anything, channelers were clearly not needed in the attack on Kandor, and it's entirely plausible that any channelers present would've been forbidden to use the OP or the TP in case someone miles distant was able to tell from the effects, a person/pigeon managed to escape or (at least with the OP) wards and/or other channelers were alerted by the weaves. An Aiel masquerade to set a false trail doesn't seem plausible, but a moratorium on channeling to avoid revealing Dreadlords is quite logical.