"Not playing as cate is taking a page right out of the Valve book for expansion packs. "
Do you mean that's good or bad?
I think it's a good thing, cause I thought valve did a pretty good job with it(though Blue shift was noticably stretching it). But that aspect works for Halflife because of the nature of the story....I got chills the first time I played and saw an area that I had previously ventured in as Gordon Freeman from a different perspective(like from the other side of the rails).
For Nolf, i think it can work as well, but for different reasons. Gone are the serious, heavy-toned opportunities to develop a story, to be repleaced by the opportunity to build on the campiness and humor of the Nolf world. As Cate, you always heard and uncovered various humorous bits and pieces of HARM policies and procedures. As a HARM operative(or better yet a trainee trying to become a harm operative) there is good potential for a game built on humor...if they have the creative talent to pull it off. For some reason, i can envision a mission to fetch a duck from a park for the new director. Why? Well, murder for hire just got themselves a goose and....