Avengers' Chairperson: Iron Man
Avengers' Deputy Chair: Miasma
Third-in-Command: Dawn LeBeau
According to the charter, these seven are the only ones qualified to lead the team ever. They are the only ones who've satisfied all of the criteria for being full Avengers. They're all "legal adults, possessing at least one skill, power, ability, or talent which is deemed valuable by majority of the active membership," who've served for 30+ days and have full security clearance. However, some others are more than qualified to take the reigns should the need arise despite not being officially able to.
Now that leaves the rest of the roster. The remainder of the team is composed of new recruits. This means they will need the sponsorship of one of the ten listed above, they have to serve a one month probationary period, and they need to pass the security check. Details on the liklihood of those criteria coming to pass are below.
NOX: There's no way in hell he could pass a security clearance; the government does not like him. Look for him to be hanging around for some time, but he won't be becoming an Avenger anytime soon!
IMPULSE: He has Iron Man's sponsorship. He's as good as in. Look for him to be moving up to full Avenger status very soon.
FAITH: Her age doesn't even qualify her as an official candidate at this point.
CRASH: She'll need extensive training and perhaps more than a 30-day probationary period, but other than that she's Avengers material.
HIMEKO: To my knowledge, Himeko hasn't expressed any real interest in becoming an Avenger. Officially, we're just housing her for the time-being since Kahn destroyed her temple.
ER'WN: Er'wn's going to have trouble passing the security clearance because he's not human. That, and his general superior attitude towards humans makes him a rather undesirable addition to the ranks anyway!