In AACW McCulloch was promotable, up to Maj. Gen.
IIRC I read, this was not carried over to CW2, bc he had never lead a formation larger than about the size of a division at the time of his death. BTW he was killed during the battle of Pea Ridge, not Wilson's Creak.
First off, AGEod is not directly representing Real-World™ ranks, but positions. For example, Jackson was promoted to Lt. Gen. before Chancellorsville, but he never lead an army. Also, in the Real-World™ seniority was a function of the date of promotion, and not an ordered list, but an ordered list could be generated through this. In some cases, dates of promotion were altered after the fact, to put one general in front of others; in some cases long after the fact. So the concept of gaining seniority is based on historical fact. But leaders who historically never reached higher positions during the war, and those who were killed before they might have, but who showed no reason to believe they might have excelled at a higher position, are excluded from promotion.
AGEod does however consider promising leaders, who were killed in the Real-World™ before they could attain the positions of the ranks they can reach in the game; for example Kearney, Reynolds, and Lyon.
We might review leaders, such as McCulloch, whether they actually ought to be promotable above the ranks currently represented in the game.
Since the game-values of leaders, who who never reached the positions in the Real-World™, which they can in the game, are speculative, one might argue, that they could have actually been better than the values at these hypothetical ranks give them in the game might actually have been better than the game values; for example Longstreet, Cleburne, and many others. Often their values take a detrimental turn for the worse, because of some incidents, which historically occurred. For example, there are some arguments, that Longstreet became somewhat dejected after his participation at the Battles of Gettysburg, Chickamauga, and Knoxville, thus his poorer values later in the game as Lt. Gen., when he might lead an army. But what if in the game he did not have such experiences? Ought he be a better leader?
It would be practically impossible to take such in-game experiences of leaders into account, simply from the standpoint of not having such a mechanism in the game engine. But one might address the situation in another way, albeit a not really historically based solution. We might have alternative leader models for some of these leaders in these hypothetical positions, implemented through RGD's.
So, let me backup a little to explain where this concept comes. In some board gaming tournaments, to lessen the affects of chance occurrences of single die roles, which are radically outside the average, which might occur at a point in the game, which would have an extreme affect on the outcome of a game, there is a special re-roll rule. Starting with one or either player, the player is given the opportunity to request a re-roll. If a player uses the re-roll, the opportunity is passed exclusively to his opponent. If the opponent used the re-roll rule after this initial re-roll, the opportunity is passed back to his opponent. In this fashion, no player can make a second re-roll, before his opponent has made a re-roll. This lessens the chance of a game being lost to a single key die roll.
In CW2 instead of a re-roll, one might allow for using alternate (better) leader values on promoting one of a set of specific leaders, who attain an hypothetical rank with poorer (purely speculative) leader values than their previous lower-rank values. I'm specifically thinking of Confederate leaders primarily, but of course there are some Union leaders as well, who might benefit from such a rule.
This would be a purely house rule specifically aimed at P-v-P games, because the game engine has no understanding of this concept, but the player might be able to use this, with some manual effort, vs Athena as well.