Philippe, do you mean a completely independent undo stack specifically for camera changes? If so, I think I agree that this would be handy. I like to get my composition how i like it (camera position and settings, DOF if required, objects positioned where desired) then I tweak materials and lighting. When I'm tweaking materials and lighting I often accidentally nudge the camera. My bad for not saving the camera by this point, or not locking it.
To be honest this isn't a major issue though - it just dictates that I should work a bit more carefully.
Thanks
Ed