1) Admirer 2) An adherent of functionalism 3) Booster 4) Champion 5) Friend 6) Protagonist 7) Supporter 
[n] - an adherent of functionalism
functionalist 1. Someone who advocates, or works according to, the principles of functionalism. 2. A reference to functionalism. 3. Built or made according to the principles of functionalism by someone who is associated with the movement.
a person who advocates, or works according to, the principles of functionalism.