Cash has a serious case of "foot in mouth" by trying to match Becker for stupid ways to make headlines. However i was his greatest fan back in 1980's heyday; even got Cash's autograph after he lost AO Final in 87 to Edberg.
Anyway Cash makes a better coach than commentator;-> when he took over as Philippoussis's Coach the Scud immediately made Final at USO(98).
Cash's biggest issue was with Lendl who he said was an absolute Wanker. Apparently in 1981 when Cash was Top Junior and Lendl was closing in on No.1 ~ Ivan saw the young dude in the Locker room & preceded to Rip Apart his new shoes that Cash's Sponsor[Ellesee] had just given him. That was Lendl's idea of a joke and putting the young Aussie in his place; like who the hell do think you are,just because you got new shoed doesn't mean you can play in the big league. Cash has stated many times that he'd like to punch Lendl if given the opportunity.
As far as Coaching is concerned I reckon Federer would be better of with someone like Wilander. Maybe Cash could do a good job coaching young Aussie Todd Reid.
Then again maybe Federer doesn't need a legitimate tennis coach; Henman did well winning Paris without one& Hewitt managed Davis Cup win without one[currently with former fitness coach].