As a proof of concept, that is very interesting. I think that Code Warrior (or something like that) can work on a server, so everyone can access it (and the number of people at the same time costs more too although it is way cheaper than separate licenses).
And on Arduino's case, the licenses are nothing to worry about, so it would really just be a repository for your sketches in the server.
I think it is possible, but the highest level my programming language skills reach is C, so I have no idea how to do it or if it's easy or not.
For the upload, XBee would work and USB too... uploading through Ethernet... I don't see it coming anytime soon, but who know?