I want it to have a hidden ending Farcry 4 style. You start out in the hospital at the end of the last game and have to make the decision again. When you let them kill Ellie, the game is over and you will see what a disease-less paradise the world will become. Or you choose the regular end and have to play the game in a dystopian hellscape.
If you demand respect or gratitude for your volunteer work, you're doing volunteering wrong.