Definitely workable but if you want better camera in VC then you may be best going for one that supports h264 or something more modern than MJPEG over USB2. If you've already got a camera then fair enough, get a cheap dongle (or spend a few quid more and get a blackmagic decklink for 99 buck/quid/whatever - PCIe though, but could use a breakout ymmv)
Sure, it was more about cost. If you already have a camera or don't mind spending extra to get one then it'll definitely give you better quality. Having said that a high end webcam can still produce good results so there's a tradeoff somewhere. If you're putting decent source material through a really cheap adapter then I think you'd better getting a decent webcam, personally but it you already have the camera then sure.