I disagree with you on a couple things..
I don't think Karpov would have buried Fischer. Fischer wasn't one of those who merely benefited from his opponents being too weak to exploit the weaknesses in his aggressiveness, like Tal for example (as some might suggest). Fischer's play was pretty sound, and he demonstrated it against all kind of players he faced in his generation (he didn't only beat them, he crushed them).
Karpov on the other hand, even though he was a great player (one of the greatest probably), he still came up short against an opponent like Fischer (aggressive, tactical ...etc.) in Kasparov, twice.. I agree that home preparation played an important role in the match (especially the one they played in 1990), but it was actually Karpov's imperfect preparation more than Kasparov's extensive preparation that had a big influence on the match (or at least the crucial games of the match).
Also, I don't think Carlsen beat Anand because of his style of play.. He's just younger and stronger. Anand at 44 is no longer Anand in 2000.. It doesn't matter how much he prepares, he's still 44. On the other hand Carlsen is young, motivated, and I heard he's pretty strong too. I don't think it mattered really if Carlsen was good in the middle game, in the endgame, if he was good at tactics or strategy, if he was an aggressive player, or a positional player, I think he would have beaten Anand anyway, no matter what his style is..