I've come across this from time to time. The idea is to rename a project and all its associated files to a new name in a simple and quick manor. I have used save as many times to do this. However, it is unsatisfactory for what is being asked for here. I would be in favor of a simple and quick way to do this.
Though I should remind you all that Sonar was one of the very first non destructive DAWs ever. In keeping with that philosophy I can see why CW has not bothered to do this. Yet its time to rethink how useful this would be for many.