I still think any person that attacks a lot or has a decent serve and volley game will give Nadal all sorts of problems.
If you serve and volley decently, you'll win most of your serving games versus anyone, not just versus Nadal.
That's not the problem. The problem playing Nadal is the difficulty to put him under excessive pressure not only when you're serving, but when he's serving too. Playing good S&V you'll win points that you would have won against any player. But don't forget Nadal is a passing shot's beast: if you S&V is doubtful, he'll punish you.
IMO, the best way to play Nadal even when your serve was not good enough to S&V properly, is making flat aggresive, high-risked shots. Now THAT puts Nadal on much pressure, he doesn't like to get the ball on the rise because that avoid him from put spin on the shot, therefore he goes back and gets too much defensive but he can't try to pass you, and that's the moment for hitting a winner against a Nadal who's lost way behind the baseline. And yes, to eventually volley if you sent him out ot the court.
To me, speaking of S&V as the anti-Nadal ultimate weapon is kinda naive. Nadal does like to defend himself, he enjoys A LOT making passing shots and on-the-run groundstrokes.
You have to make him go SO defensive that he won't enjoy that any more. And the players who did it more succesfully were players who attacked Nadal with flat, deep shots all of the time. Of course that's a risky strategy and you need to be absolutely "on" in order to be able to beat him (i.e. Tsonga at 2008 AO, Ferrer at USO). Nobody says that strategy is easy but we're talking about the #1, you can't beat the #1 without taking some risks. It's doable. It's been done before.
Playing much S&V is like saying to Nadal "c'mon guy, show me your passing shots and those strokes on-the-run, and enjoy it".
Playing constant deep flat groundstrokes is like saying to Nadal "you like to run and be way back the baseline? You'll run as never before in your life and I'll take you 100 kilometers behind the line"