i think andy's best chance of beating federer is to beat him like he always has, by making him play a ton of balls and playing great defense. 'attacking andy murray' surfaces in spurts, but is largely a myth. murray is a brilliant defender and that sort of player, historically, has troubled roger (canas, andy, nadal.)
keep the ball deep, frustrate him-federer is not a model of consistency from the baseline.
i just don't see andy murray doing a better job of attacking roger than vice-versa. other than the serve, of course. andy absolutely has to serve well, that goes without saying.