I think that making different versions of players may prove useful to fit diferent teams in diferent times.
Take Ronaldo Fenomeno, he was probably at his best in Barcelona? but he won Best Player of the World award while in Inter and while in Real Madrid. And he changed his way of play during these times as the stats (there are 3 Ronaldos in this database) accurately portray.
This logic, in my specific case, I've applied it to Figo and Cristiano Ronaldo, both of them played in Sporting in the early stages of their careers and, of course, were a shadow of what would become in later years. But if I want to play with Sporting from that time, would't be fair to have Figo with the Real stats or Cristiano Ronaldo with Man Utd stats. They suffered a natural evolution troughout the years and were inferior players at the time.
This to say that I personally stand with different sets of stats for the same player to emmulate different times of his career.
When the seagulls follow the trawler, it is because they think sardines will be thrown into the sea. Eric Cantona