The biggest problem with ascribing hard game mechanics to military rank is that it'd be way too hard to standardize against different play styles for different play groups.

There are all sorts of things, such as the timing of sessions and how much of a time frame they cover, to how much time passes between sessions, not to mention the actual roleplaying that can't exactly be rules-codified.

I like the Alliance Contribution table, myself, which--to paraphrase the words of Captain Barbossa--is more like guidelines.

Of course, rank doesn't always mean much of anything to those not under your command. The Rebellion isn't truly a single unified command, so whoever gives you rank gives you authority over their own assets, and the other allied commands can choose to recognize it or not. There's also the differences in types of ranks. Line officers are going to be different from staff and support officers (a doctor with a rank of Major doesn't hold command over a unit of infantry).

Looking on Wookieepedia it looks like the alliance had the following breakdown for the army/navy.

Trooper / Deckman

Corporal / Petty Officer

Sergeant / Sr Petty Officer

Lieutenant / Ensign

Captain / Lieutenant

Major / Lt Commander

Colonel / Commander

General / Captain

Admiral

Hmm... As far as I am aware naval Captains are traditionally roughly equivalent to army Colonel, rather than General. But then I guess they don't have Lieutenant Colonels (usually equivalent to naval Commanders) and they don't seem to have intermediary ranks between Colonel and General (historically that is quite some jump up).

I certainly wouldn't leave the ever cool "Brigadier" out of the rank structure.

Oh, and of course, regardless of rank an officer in charge of a vessel is always referred to "Captain" while on board ship.

I actually geeked-out and looked up Captain Needa on imdb, and he would have been 41 when shooting ESB. So 22 years prior he would have been... 19! I guess it must have been an unpopular war, if they had to put teenagers in command of capital ships.

Even if he was 41 he might have been playing some one who was 50, Frank Oz wasn't 900 when he played Yoda, lol.

But another point about rank is that the rebellion is kind of hodge-podge. You have Dressellian militia fighting along side ex-Imperial commandos and a former Wookiee commander from the clone wars who became a slave before being freed and a princess of a dead planet (Han's strike force). You can't really think of it as a single force, its more like NATO, there is one person in command but beyond that each force has its own ranks. You may have been a Lord High Commander in your home systems militia but then you join the Rebellion and are put on Solo's strike team and now you have to serve under a wookiee cause he's the second in command? lol

Looking on Wookieepedia it looks like the alliance had the following breakdown for the army/navy.

Trooper / Deckman

Corporal / Petty Officer

Sergeant / Sr Petty Officer

Lieutenant / Ensign

Captain / Lieutenant

Major / Lt Commander

Colonel / Commander

General / Captain

Admiral

Hmm... As far as I am aware naval Captains are traditionally roughly equivalent to army Colonel, rather than General. But then I guess they don't have Lieutenant Colonels (usually equivalent to naval Commanders) and they don't seem to have intermediary ranks between Colonel and General (historically that is quite some jump up).

I certainly wouldn't leave the ever cool "Brigadier" out of the rank structure.

Oh, and of course, regardless of rank an officer in charge of a vessel is always referred to "Captain" while on board ship.

Yea, I don't like that structure, it does feel like a rank or two is missing. I'd go with:

Trooper / Deckman

Corporal / Petty Officer

Sergeant / Sr Petty Officer

Lieutenant / Ensign

Captain / Lieutenant

Major / Lt Commander

Lt. Colonel/ Commander

Colonel/ Captain

Major General/ Rear Admiral

General/ Admiral

Especially when we have evidence of the rank of Rear Admiral and Major General being used in the fluff.

While it may not be a full list, and depending on your opinion of the EU, Starfighter command has the following ranks in this order (may not be full list, may be some between these):

Flight Officer

Lieutenant

Captain

Major

Colonel

Commander

General

Source: X-Wing novels. (and yes, it is Commander over Colonel, I know it seems odd, but Wedge was a Commander, which was the top rank allowed to keep with a starfighter squadron. After he finally accepted a General position, Tycho is promoted to Colonel, and still allowed to stay with a starfighter squadron, which obviously implies that it was below Commander).