@Evil Dave
I haven't played Neverwinter Nights, but I understand that its tactical space is also pretty large (300+ spells). Also note that they were starting from square one, with all rules equally-weighted, to test out the effectiveness of dynamic scripting itself. In practice you'd probably be starting from a known rulebase that works against "most players." But yeah, it's unlikely that this would produce a truly intelligent AI--I'd settle for merely an adaptive one, so that it's no longer meaningful to talk about how to beat "the computer" but rather "this computer."
Plus, I think the idea of AI programming metagames is a fun one.
-M.D.W.