Ya i've been thinking the same for my HV20. it should be strong enough. the camera isnt all that heavy and the shoe is made of metal. just make sure you have one that can tighten so that the camera doesnt fly off by accident.
the canon hv 20/30 have top stereo mics though. your hand would mess up the audio if you built a handle or used a mic. that first handle looks awesome though.... plans? or is it really as simple as it looks?