I appreciate the point about Neverwinter Nights, and if the Dominions AI isn't internally doing scripting I guess it wouldn't be trivial to make it learn. Still, I wonder if the PBEM aspect of Dom3 offers enough "hooks" to build a scripting AI client anyway; you'd have to know how to write .trn files and, as you pointed out, how to read game state like "who controls province #33 this turn, and how many units do I see in it?" and "What items is my Pretender carrying?" It doesn't necessarily have to tie into the existing AI engine, but at least in principle the PBEM orders/execution/results division offers everything you need to write a learning engine.
Even if it did have to wait for Dom4, which I hope it doesn't (I'm off to look at my .trn files in a minute and try to figure out what's in them), an adaptive AI would be incredible for us SP folks and a real selling point. Not that Dom3 is lacking in selling points.
Terrific game, even if I just discovered it three weeks ago.
-Max