What would/did happen to trainees who never got a spot on a Superhero Team (due to no vacancies, or maybe being pregnant when a vacancy did appear)? Was there any stigma to that?

emeralddodge:

There were always vacancies, since team members were constantly getting cycled out because of age, injury, pregnancy, etc. However, theoretically the camps would’ve asked Bell to eat the cost to the city that took the extra superhero. 

In such a situation, there would’ve been an enormous stigma.