Hmmm can't help you with bike choice. Wellington has lots of hills around it so if you are riding fixed, you'll get to have the whole 'frisco boys experience. Maybe you can do a blog on downhill spinning, macaframa style.
haulage-wise, you'd be surprised. With many airlines they'll let you take sporting equipment as extra luggage without charge for long haul flights. I'm flying virgin to Aus and they have confirmed there will be no problems with me taking my bike on the plane. Weight limit 32 kilo (more than normal luggage!). So that is 9kg for the bike and another 20 in clothes, shoes, tools that I'll squeeze in. Nice.
Re hong kong stop-over, they have an oversize luggage service at the airport there, you can drop your bike off there for a few days. I dunno the daily charge but will find out in a week, ask me after that.