Had an Army Colonel make such a suggestion one time in an Aviator's Safety Conference....said comment resulting from his opinion Rear View mirrors would prevent Tail Rotor strikes while hovering around trees, bushes, mountains....etc.
A very crusty old CW4 who had started his Army flying in Korea reckoned the Colonel was on to something....and opined that done right...with mirrors on all four corners of the aircraft the Colonel would be able to see the back of his own head if he tried.
Exit one very unhappy Colonel after the Warrant Officer chorus soundly applauded the old fart's comment!