I guess that is what tail lights are for.... I kinda see it like fog lights are to give a little discrete visibility when it'* foggy or in a semi-low light condition. This being the case we don't spend enough time in reverse to warrant rear fog lights....

yes but i would love to move it into the cluster in place of one of the reversing lamps

i would think it quite easy to do just put a live to live on the indicater side then the other side just put to earth