I remember Bill Lawry - or someone - comparing Brad Haddin to Mark Waugh during the course of that breakout century he scored against New Zealand at Adelaide in 2008/09. The comparison was on the basis of the fact that even though he'd have been far best-advised to let Daniel Vettori bowl over-the-wicket, pretty harmlessly, at him and feast on the rubbish served-up by the rest of the attack, Haddin seemed near-incapable of doing so, and instead tried all sorts of innovative strokes against Vettori. Obviously, it did him no harm in that particular knock, but it could easily have done and in similar circumstances repeated would do, plenty of times.
I often wonder how good Mark Waugh would've been with a different attitude against spinners. Against seam he played the ball on merits, almost without fail (unless the team was on 350-2 or so). But against spin it was different. Was it arrogance? Sometimes it almost struck me as mere boredom - something always had to be happening when spinners were bowling at him. He was, when he played the ball on merit, one of the best players of spin I've seen, especially among Australians.
You're very right that we have no way of knowing whether it'd have, on the whole, been a positive or negative on his batting had he been different - it could easily have been either. The same applies to many similar free-spirit players - I always say to those who lament Ian Botham's attitude that had he been more of a knuckle-downer he might well not have been as good as he briefly was.
Mark Waugh was what Mark Waugh was. It's funny that he did manage on that one occasion to play Warne on the ball and not merely the fact that he was a spinner. I wonder if there were others.