I read an article about Johnny Mac offering himself as Andy's new coach in a round about way. He's a great master of the sport and his expertise/experience is quite valuable; however, Andy made it quite clear that he won't be hiring any tennis legend as his next coach. So I guess that possibility was always out of the question.
http://www.dailymail.co.uk/sport/tennis/article-2618291/John-McEnroe-contention-Andy-Murrays-coach.htmlA new coach really should be someone who brings different perspectives and strategies vs other players since that's what mostly it's about. And also, he can tweak Andy's game a bit where it's necessary but most importantly, keep Andy highly motivated if Andy is still willing to play at a very high level throughout the year and throughout his career overall.
Someone who's willing to travel and be very keen on Andy's needs and the way he wants things. But at the same time, he should be able to instill new ideas into that stubborn mind of Andy. Perhaps that will require some subtlety.