The only full back who offers just as much in attack as he does at the back is Maicon.
That's the player you all have as a role model when you look for a Grygera or Molinaro sub, but let me tell you that you won't find him.
Those who want Grosso, Danny Alves, Zhirkov or Lahm will say that Abidal or Clichy don't offer much in attack. Those who want Abidal or Clichy will say that Grosso, Alves and Lahm suck in defending, just to prove that the French Lb's are the better choice.
Since we can't buy Maicon and there isn't another Cafu or Zambrotta (the old one), we should ask ourselves what is it that we need more from the RB/LB? To attack or to defend?
Like i said few days ago, i see the back players primarly as defenders and only then i want them to help in attack.
Juve is not the team that can afford having Danny Alves, as good as he is. Barcelona has all the possession and Alves can allow himself excursions in attack, without comming back to cover (which will sooner or later cost Barca a lot), but if such a player plays for Juve then may God help us, with all the space he'll leave behind.
What i want to say is that i want a Thuram at RB/LB. He also wasn't brilliant going forward, he didn't make great crosses. But he was a rock at the back and he was still everywhere on the right side, ready to help Camoranesi in attack but always covering his side in defense.
That's only my opinion, though. It doesn't mean i'm right. Some of you think that we need a crosser more than we need a defender and we'll have to agree to disagree on this.