The longer I think about it, the more certain I am this whole 'head coach' business is just a marketing stunt.
Becker's only task will be to improve Djokovic's atrocious overheads, together with his volleys.
The biggest problem with Becker is that he's very self-orientated, and loves to talk about just how wonderful he and his career was. I'm not sure that he's capable of actually putting another player first and thinking of what is actually important for him.
I think it could have worked as an advisor, or consultant or whatever, so that it's only supposed to be temporary or specific to certain aspects of his game. I'm wary of it going all Sharapova/Connors if he's supposed to be a permanent coach.
He'll have seen how much respect Lendl has been getting lately and will want in on the action, but one of the things that has made Lendl a great coach is that he knows when to shut up, and neither he, nor Murray are attention seekers, so there weren't problems with ego.