Two points:

1) Kahneman's model is probably too high level to apply to solving NLP problems. It's an interesting abstraction, not a road map to human reasoning.

2) System 2 is Effortful Reasoning, not just doing math. For example, if you were engaging system 2 to plan how long a project was going to take system 2 would think about what kind of questions were relevant to generating an answer (how long have similar projects taken, are there any differences between this project and the others, etc.) and then think about how to combine these to produce an answer. Computers do not perform this kind of reasoning well at all.