Hey UDN,
Would it be possible to add a new view mode that would allow you to see the mip level changes of textures as the camera gets further and closer to objects? This new view mode would replace all objects currently applied textures(Probably just Diffuse/Albeto) with a texture representing the current texture mip level size. Then as you moved your camera throughout the scene the textures would change based on what level mip map level the objects in the scene are currently using. I think this would allow you to better tell if you are in facing using all of your mips maps appropriately and might even help in making sure that your textures are not big in relation to whats on screen.
Cheers-
Sam Deiter