We've shot the HF20 underwater in the WP-V1 housing and it worked fine. I wouldn't consider it overly fragile, it's just not made from the thicker plastic as Ikelite which costs more to do. The Gates and Light & Motion housings are made form machined aluminum, which costs much more to produce and are produced in much smaller numbers. Also the other brands tend to have more controls, and each additional control adds to the cost.
The housing has a 67mm threaded port which accepts the popular 67mm wide angle conversion lenses form companies such as Inon and Ikelite. You can also add a color correction filter.
Stix is coming out with a tray system for this housing that will have 2 ball mounts for lights. I can suggest the Fisheye LED 1000 lights, as they are self contained and small relative to the amount of light they put out. The handles and tray system carry the weight of the housing and lights, so there's no extra stress on the housing due to using arms and lights.
I'll try to get pictures up of everything as soon as we get the products in.
Best regards,
Jim