Is it possible to show the Full name instead of Username if the user has entered a Full name?

I'm asking because I'm using the Write API to create users and is supplying a made up username in the registration process. Later I'm using the shared sessions plugin to login the user.

However, I want the user to be able to change the screen name since the Username is made up and not very pretty. I have disabled Change username since I can't sync these changes back to my main site where I set the JWT cookie required for shared sessions plugin to work.

Is it possible without changing a lot of lines in the .tpl files?

Thanks!