Second Life's spiritual successor, High Fidelity (now dead as a commercial project, but which lives in our open source fork overte.org) does something like that

Second Life's spiritual successor, High Fidelity (now dead as a commercial project, but which lives in our open source fork overte.org) does something like that. The server picks a client to do the physics for part of the world. It's pretty clever and means a very light server can go a long way, but the downside is that physics gets unreliable. One of our plans is to have an option for a SL-like model where the server is again in charge, for scenarios that require security, reliability, or physics to keep running in the absence of clients.