You don't "add" talent, you improve on what's already there, that's why I say talent is not nearly the most important in a player. Federer has more natural talent than Nadal, and IMO so do Murray and Djokovic, and it all means absolutley squat, because Nadal owns them all in mental strength, agility, and consistency. Again, Gasquet has huge amounts of talent, not any less than Federer (which is saying a lot), but that talent got him nowhere, because he lacks a lot of things that build a great player, such as fitness, tactics, mental strength, etc. Talent alone is not enough.
Federer can improve sure, he's not perfect, far from it. All I was saying is that because of his natural talent things were a bit easier for him than for Nadal.
Fed never struggled on clay as much as Nada struggled on HCs at first IMO. In fact, Fed reached a clay GS final before Nadal reached a HC GS semi final (despite having two of those). Would Nadal dominate back then? I seriously don't think so.
Roddick and Hewitt are great players. People make Fed's rivales back in the day look weak, but they hardly were. Safin and Nalbandian are IMO more talented than Murray and Djokovic (and Nalby proved he's a tough matchup for Nadal and Federer, and can beat them both when he's on), and the fact Fed has a winning record on them both (in their primes!) is amazing. Of course the same applies to Roddick and Hewitt.