Regarding the gamemaster, I think we absolutely need one. It can be the same for each story, or change from one to another, it’s the same, but he/her must be one that has a grasp on the past history and keeps track of every detail in the current story. The last story, for me, is the perfect example: it was very fun, but also very slow, and many things were quickly forgotten/abandoned, until Kristogar bring back all and gave them a cohesive meaning.
So, I don’t think that the one which begin the story is automatically the master: each one of us must have a chance to start a story (not to “tell his story” because that is possible only in solo tales), but not each of us, for lack of time or other things, can be committed to story to be the master.

About the leader, if they are a group of friends living in an island, obviously there is no need of a leader.
If they are “professionals”, they need a president and a board of administrators (plus a secretary, yes). The president is actually a leader for the team, at last regarding the “outside” world, and it can change, trough elections, each year or so. For me, the only one suited, at the moment, for the task, is Kristogar. He seems to know the metahuman world, he is/was involved with the researches about the metagene, with TriVex and the USA Government, and maybe also with aliens (see his first post). In time, the others will gain much more knowledge/confidence, and someone other could take the role of president.
Field leaders, on the other hand, can change with every story, accordingly with the “theme” of the story. If they fight demons, Naecken will lead; if they travel to other dimension, Mxy is the obvious choice, while in the slums of a big city, Pete is the best suited, and so on.
And it is not only the skills to claim for a particular person to lead, but also chance (if Kristogar has been captured, someone other have to take his place.

Anyway, just because they are rookies, they need the only experienced one, Kristogar, to act as a leading figure. If not leader, call him babysitter, but the last story, for me, has proven it, in term of play and storytelling.

BUT, I am not on the team anymore, at last for the moment, so I don’t think to have the right to say how the “Revolutionaries” should behave…