Well...
It sounds like a good idea for the UU Store probably (as they do sell Ukulele's in their store) - and if people are concerned about things like "Who's playing the Uke?"...well I would assume that if the maker of the Uke, or the UU staff, were to make a video/sound sample of each Uke (probably not each with diff strings though), then that could at least help in understanding how a Uke sounds.
How it sounds doesn't automatically guarantee a purchase though of course! I have never bought an Uke solely off how it sounds - I have to TOUCH and FEEEL the Uke, BE ONE WITH THE UKE...(k, maybe that's taking it a little too far, haha)
Overall, for the store...it'd be a good idea. I mean, other websites do it, right? Even MGM has some vids on his auctions showing how the Uke's sound.