I remember back when it was first released, Niantic would change the teams of some players if the player emailed them. I wish I could verify if this was still the case or not, and I believe it was a one time only deal.
Yeah, that would be interesting. I joined valor, because it was the colour of the gym closest to my house, and I didn't realize at the time that that would change
Now I wish I chose an instinct, because they have the least gyms in my area, which means I could have many more targets for takedown.