The Age of Rebellion RPG has a bunch of details that make it challenging to stat up "starting" PCs for the various Tierfon groups.
Within the command structure at the base, beings have different ranks, which leads to different "Contribution" ratings. Presumably, the only way these beings arrived at a higher Contribution scores was by accruing "Duty" during adventures (or by some other means? More on that later*). Thus, higher ranking individuals should also have more XP (seems to make sense) and thus will be less likely to be an appropriate starting character for new PCs (also seems OK).
Some of the highest ranking personnel at Tierfon (Major Moorla, for instance) should be statted up as NPC "Adversaries" of some kind (Rival or Nemesis?). Others could be playable PCs (Black Squadron pilots, SpecForce team members).
Another wrinkle added to the complexity that is Tierfon, Troupe Style!
*Maybe not. Perhaps there is a different, longer term track for NPCs to gather high Contribution rankings. After all, one might not expect Mon Mothma (who arguably has the highest Contribution rating possible!) to be a top-notch PC. (I hope she couldn't beat me up in hand-to-hand combat!) I'm sure she hasn't trained with blasters, for instance. We're talking about a former Senator, now chief diplomat. I guess she could be seen as something like a maxed-out Diplomat PC or something?
Another take on this: the most inexperienced starfighter pilot (fresh from "the academy") is still an officer, thus, they technically have (just starting out) a quite high Contribution rating. This makes some sense, as the Alliance will have invested a lot of time and effort into their training, and handed them the keys, so to speak, for some very expensive equipment. I would guess they'd have beginning characters, stats-wise, but higher than average Contribution right from the get-go.
Similarly, if any PC of any type is allowed to know the location of a top secret Rebel Alliance Starfighter base (and can actually go there) they must be trusted by the Alliance a fair bit. According to table 9-3: "Group Contribution Rank Guidelines", an Alliance soldier isn't really a trusted member of the Rebel Alliance until they reach a Contribution rank of 2+. One could almost argue that everyone at Tierfon better be in that category. I also would note that SpecForce personnel should have a "higher -than-their-rank-would-suggest" value for Contribution. At least a +1 bonus for enlisted soldiers.