I agree, but there's something to consider.
Neverwinter Nights was created with the goal of bringing D&D gameplay into a credible video game world. Think of it this way: Bioware first created the engine and then breathed in the content, the story, the characters etc. So the engine and the gameplay is more important than the story.
In KotOR, the story has the importance - the characters, the quests etc. So Bioware made that first and then used the engine for NWN. So the goal is to create a more entertaining experience, rather than a technical game.
The toolset was included because NWN is a very, well, divided game. You can separate each of the game's components and have them work the way you like, and modify them. Hence, there was lots of modding potential. In KotOR, the engine isn't that blocky and is more integrated. The developers wouldn't see much modding potential in a adventure-themed KotOR and so... well...
I just don't think it'll happen.