The thought has tickled my mind several times, but until I get support for multiple windows into GLFW I don't think there is much use to do the GLUT emulation layer. Another key point is the support for callbacks for redraw events and such, plus the long overdue glfwWaitEvents() function.
So basically, with release 3.0 of GLFW (which will not happen until "all of the above" has been implemented), I suppose it is ready to host a more or less complete GLUT emulation layer. Perhaps not 100% compliant with the GLUT spec, but it should compile and run most legacy apps, I believe (which is what should be the goal, imho).
Alos, since I like to keep GLFW minimal, I think the best way is to make the GLUT emulation layer as a separate lib, or at least as a compile time option.