Yeah, I like that.
It'd still potentially be a bunch of info though and whether you'd transfer it peer-to-peer (which could be very slow and would be a bit error prone methinks) or have your client upload it to the server would be an interesting one.
Sounds like the kind of thing that would perhaps best be done by mods? Presumably when I'm connected to a server with you and you've got a custom skin, my client gets the skin (file?) name... Could a mod tell that my install doesn't have that skin and attempt to fetch it from http://awesomedcsskinsmod.com/, where you've uploaded it?
Just riffin'... :-P