As a Nadal fan (though not a fanatic) this is what I would do if I was in his shoes. I would continue playing my game, and just eliminate 90% of the hard court tournaments from my schedule. Meaning I would show up at the US and Australian Opens, and maybe a couple more, nothing more. This would elicit enormous criticism of wimpiness and incompleteness, no doubt, but if the alternative is to cut your tennis career short by ruining your body, I would consider it the most reasonable alternative.
Nadal has the game he has, and that's the game that brought him to the top. You can't radically change the way you move without simultaneously having to change all other aspects of your game. He can actually play pretty well on hard courts, and he has shown that he can, but only at the expense of great physical damage to his body. By now it has become a clear pattern that, come hard court season, his body starts to give him problems.
On the other hand, his movement is very well suited to the natural surfaces, which can absorbe much of the pounding away from his bones, so he can play loosely. I used to think he does not know how to move well on hard surfaces. But in fact he does. What happens is he has learned he has to be much more careful how hard he treads, and he can't afford to be as loose as he is on clay and grass, hence the appearance of something awkward in his movement.
Hard courts are pretty brutal, but they are more brutal on some than on others. Since it is probably unrealistic to think they will ever be eliminated, a player should have the right to radically reduce, or even eliminate, how much he plays on them. The tour is heavily tilted toward play on hard courts. Hard-court raised American players have traditionally avoided most of the clay season, and that's considered acceptable. Why wouldn't the opposite be acceptable also? A poster here recently stated that hard courts are not a specialty surface, like grass or clay, but rather the natural surface that God gave to tennis. This preposterous view seems to be widespread.
I am not familiar enough with the details of the tour rules, but it seems to me that a player attempting to radically reduce hard court tournaments from his schedule would be severly penalized (and criticized) and have little chance of staying at the top, but maybe am wrong. On the other hand, players like Sampras never gave much of a hoot about clay, and managed to stay on top.
I am straying away from the topic, but something there seems not quite right. The bottom line is this: I enjoy watching Nadal play, especially the way he played when he burst on the scene in 2005, precisely because of his heavily physical style. Nothing like that had ever been seen. (I also enjoy watching Fed for a completely different style). But I am now observing that, in his attempt to adapt his game to hard courts without ruining his body, his signature style is being blunted, and am afraid this may in the end affect his tennis on the natural surfaces as well. Between seeing Nadal play great clay and grass court tennis for 8 or 10 more years, and seeing him ruin his body in 2 or 3 by playing on hard courts, I'd choose the former anytime.