Disagree about Xavi. A very good player but a very specific player. He wasn’t technically good enough to play any other way. What he did, he did very very well but you wouldn’t pull out the tactics and tell him to change because he couldn’t.
Ironically, this is what I think about Iniesta, not Xavi. Xavi was always brilliant. in the 08/09 season, with more open spaces, he was making so many penetrative passes. He had the best press resistance, count hassle better than most midfielders, his positioning was top class, and that's before we talk about the things that made him truly special.
The agility to hold on to the ball and turn into positions that gave him space to assess. His head swivels that could accurately detect space. The pinpoint accuracy and shapness of his short passes. I think in another team, Xavi may have ended up being a slightly different player, but he would have been just as good.
Iniesta on the other hand, I don't really think so. His game relied heavily on how lateral Barcelona's game was. Yes, he we was sort of an outlet for players who were struggling to keep the ball in attacking positions, due to his brilliant roaming. However, due to most teams not actually having the opportunity to make space for multiple roaming players, on another team, like United in the 2000s, I could easily see him being isolated out of games. Even at Barca, he wasn't what he became until Pep turned up, Rijkaard who was another good possession manager struggled to use him as effectively. He had good balance and agility, but I don't think his strength would have allowed him play in a no.10 role in England or Italy. He's also not the final ball player like a Fabregas could be. My take would be, on another team, even at Real Madrid or Atletico in La Liga, I don't think Iniesta would be considered that important to his team due to them not being able to use him like Barca did. Furthermore, some people might cite David Silva. However, Silva was an exceptional player who had similar attributes, but I think he actually dictated games more than Iniesta did. Where Iniesta is more of a relief for surrounding attacking players, who could occasionally drive when provided with space and could thread that through pass from the left inside space on occassion, Silva was more of a constant threat and playmaker. He would seek the ball to create one two and then have it back. He would use his agility, balance and off the ball movement to create space, retain possession, dictate tempo and create chances. They had very similar skillsets, but I feel Silva used it in a different way and I can decisively say if given the opportunity that Iniesta could have played in this way.