An editor has now been added in v0.6 to allow you to add new teams or make a copy of existing team data so you can make changes and override it.
This means you can change the names of players to reflect real names or even create entirely new teams from any year from 1960 to 202x such as Premier League, La Liga or you local pub teams.
If you create something special then why not upload it to the Steam Workshop.
Check out the guide for more details.
If you have any queries then please head over the the Discussions are.