Yes, i have used a similar solution, but this doesn't use the built-in GL_DEPTH24_STENCIL8_EXT. Having a separate color buffer just for stencil information seems very unnecessary.
What is the correct way of getting the stencil part of GL_DEPTH24_STENCIL8_EXT, if i wish to display the stencil buffer on screen? If i have omitted any important details of my implementation, please tell me and ill give more information.