I made a mod just like this for me and my friends. When a hero buybacks their name is announced like they would pick the hero. It's great and have saved me many times, however it's not found here on the forum because I can't be arsed to zip the mod etc, write a fancy thread and keep it up to date so noobs don't go crazy.
So on the question of possibility? Very possible. Is it an advantage? Not really. You can see it from the scoreboard so why would this be unfair?, a mod is just a way to take the information that is already displayed on your screen and change it, modify it do display in a different way.