Editing existing players

In game editing question rather than a creation centre one, as I'm aware you can't edit or assign EA created players with creation centre already.
Is it possible to edit traits and personalities for existing players?
As expected EA don't do any proper research outside the top divisions and don't really care if championship players are renowned for arguing with refs etc, just the odd key player per club.
I would like to run through the Leeds line up and assign certain abilities and correct a few issues. Biggest example is how under-rated Davide Somma is, which to be fair, I fully expected as he's only really broke through this season. I can resolve the basics, give him a much more powerful shot etc, but what I can't do is influence the traits.
Another example being Max Gradel, perhaps the most enthusistic, hard working, selfish player ever who always tried to beat his man but without being especially skillful. He's got none of the traits assigned to cover that off, which if there would leave me to reduce his actual ability slightly.