I'm at the end of my first season playing, and getting daily reminders to resign my players who are in their last year.
Yet, the only option to sign players is to change their salary cap hit, and raise their bonus, for the current year. This would put me over the salary cap.
Their needs to be an additional Extension option, which would add years to the end of the current contract, rather than changing it.
This would also give us teams that don't make the playoffs something we can do while waiting for the end of the season. Right now it seems there's little reason to sign in, unless we want to watch someone else's games.

Extensions would be ideal.

You will find though renegotiating that last year will increase your available salary cap this year. For a good portion of your 1 yr players.