The suggested assignment, the Virtual Dealing Room, incorporates all the challenges mentioned above. It is ambitious, indeed, but certainly relevant, since virtual communities will become a dominant phenomenon on the Internet. It is an example of a knowledge-intensive, distributed application area, for which O-O provides, in principle, the solutions required for their realization.
Of course, you are welcome to think of variations on this theme.
If you think that the technology will be too much to master, don't worry. This will usually be sorted out.
Although it would be nice to have a real 3D interface to the community, I am aware of the fact that most of the technology involved is still somewhat unstable. See MMA1 Web3D for more information on VRML/Web3D technology. However, even without using 3D technology, you must strive for an intuitive interface that that is suited for the application domain.