i think defensive scout makes more sense than passive scout.
I dont think its really necessary to have passive/aggressive scouts for anything other than mid fights. if your passive scout has it stuck in his head that he has to play passively then he's going to skip out on a lot of opportunities.
I think you should only have a passive/aggro scout system when the players naturally play that way. Also, i wouldn't underestimate the importance of your passive scout having good dm because he's the one protecting your demo, who is the 2nd most important person on your team. Passive scouts need to excel at mid-range scattergun aim so they can deter opposing scouts from aggressing on their demo.
EDIT: HOLY SHIT I FUCKED THAT UP LOL