I honestly don't see Cliff being with the modern day Metallica at all. If he didn't die I think he would have left the band long ago. I think he is more along the lines of a Dave Mustaine who loves the music more than anything else.
I would see Cliff doing Metallica covers or having his own band with him in charge that didn't hit the mainstream. Just my
BTW Check out Dead Horse if you are looking for some killer drums and guitars. You can get their album online at emusic.com its called "Peaceful Death and Pretty Flowers".
Really good.