Well there's the thing. I've been planning this trip for quite a while now, making changes seemingly daily. I finally got to a point where I thought I'd got it pretty concrete so decided to check with the experts... and now I've got brand new ideas for both the start and end of the trip - I think I'm going back to the drawing board.
Thanks for the recommendation of going out to NRT via HKG. The main reason why I was routing straight out to NRT was that our trip starts in September so I wanted to get to Japan in the Autumn - but I suppose a transfer, or even stopover, in HKG on the way wouldn't hurt.