Would be a token, rewarding all the effort we put, sometimes grinding 39 levels to unlock a weapon we wanted, like the StG-44. A toil which, with the new updated, gladly no longer will be required.
I feel like a veteran, mastering a campaign in the current (soon to be old) system. And I wish to show that to other players. A nickname decorator, or a unique portrait, specific to each campaign that was maxed out, would do the job.
I know this will require some work from the developing team artists, but it would help make players who played that long to feel appreciated.