Although I like this idea a lot, as I'll note later.

The start of ythe series was full of grey tones, so that anybody - Perrin, Mat, Lan could all be DF. Thom, as the *complete* outsider in the group (the only guy who's alone), was the most extreme example of this. Even up to TGH, he might've been a crafty agent for evil.

In fact, his attack on the Fade in Whitebridge (and his weird survival of same) was one of the greatest double-bluffs I ever read. He could've been saving the boys from awful death in noble sacrifice; or he could've been play-acting. He comes back, and he helps when the leads are surrounded by DF, but he goes on to murder a king from (rightful) revenge Awesome.

Still, the actions of Thom in every subsequent pretty much pull him out of the Darkside. There's too much that we would have to fold into the plot twist, or ignore, for Thom to still work as a character and be the best deep-cover agent the Shadow has in this Age (because Taim is freakishly obvious).

However, I would totally love it if you were right - I'd think the firs tbig change would be that Thom - not Noal - was the old man with weathered fingers who's watching that place in Ebou Dar. Lovely.