McCullum is a match winner. I have absolutely no desire to see him radically change his game to someone who unnaturally grinds out reasonable scores on a regular basis. In the past 12 months he has scored two double centuries and one triple century*, all three innings being telling factors in us beating esteemed opposition, both home and away.
The likes of Williamson and Taylor, possibly Latham now too, are there to provide some solidity and a platform to our innings. McCullum is there to win us tests. Because he can make the difference in any innings, in any format too. That is why he is world class.
*I realise the 300 did not win us the test but it is possibly the greatest match saving innings of all time and did secure us a series win over a top 4 test side.