Re: Metallica with Cliff....
At a guess, I reckon they would have followed a very similar path. It wasn't as if Newstead decided the direction of the band or even made huge contributions to the song writing and overall business decisions. Even when Cliff was still on board, it was James and Lars that had creative control. Pretty much the way it is now is the way it's always been.
Nup, personally I think the path they followed post Cliff Burton would have been reasonably similar to what would have happened if he hadn't been killed. Kirk Hammett was there then and now. He's said himself that ultimate control lies with Hetfeild and Ulrich.....or to paraphrase him, he said something like: I'm under no false illusions as to my place in this band. I can't see that Cliff would have had any more impact on their decision making than Kirk to be honest.
It's an interesting theory but I just can't see it being any other way. Regardless, it's all just speculation. He's long gone and Metallica are what they are.