I haven't seen this brought up in the Chinese discussions yet, and I'm not sure if English fandom have addressed this, so I'm throwing out my own over-thinking of Xianzhou lore...
In the Xianzhou fleet PV, we get lore stating that there's one marshal and 6 generals. Each general leads a ship and, if Luofu's naming convention is anything universal, the military unit is called "云骑军". (According to Bilibili game wiki, the 云骑军, or Cloud Knights in English translation, is universal across all six fleets. On the other hand, the Bilibili wiki also claims there's no universal leadership across the six ships...nor is the marshal clearly indicated, but we know that the marshal does in fact exist above the six generals in terms of military officer rank.)
Anyway, weird contradictory details aside, I'm thinking about how each ship has its own "corps" so to speak. Quick military basics: the military personnel are organized by grouping smaller units together into bigger units. In modern US military, the grouping goes (from small to large) squad, platoon, company, battalion, regiment, brigade, division, corps. In modern Chinese military, the military is similarly grouped into (from large to small, because the order is reversed in China) 军、师、旅、团、营、连、排、班. So, 军 could also refer to the size of the military organization, which is the equivalent of the US "corps". So instead of just "Cloud Knights", it could be read as "Cloud Knights Corps".
And yes, Luofu is based on ancient China. But see, in ancient China, the military organization is (again, from large to small) 军、师、旅、卒、两、伍. You will notice that 军 (and 师、旅) were retained from old ass times. (Trivia, the order I listed is lifted from the Zhou dynasty, this is going to be important later.) So, regardless of modern or ancient reading, each fleet can be read (in Chinese) as hosting a "Corps" of the greater Xianzhou military.
Now, if we use this interpretation of the word 军, then this brings up an interesting historical reference. In 《周礼·夏官·序官》, there's this passage:
王六军,大国三军,次国二军,小国一军。
This roughly translates to King (in this case 周天子 aka Zhou King) possesses six "Corps" worth of military power. Large fuedal states have three "Corps". Secondary feudal states can have two "Corps". Minor feudal states can have one "Corps".
This claim is corroberated by 《左传·襄公十四年》, which states:
周 为六军,诸侯之大者,三军可也。
Which roughly translates to Zhou possesses six "Corps" of military might. The higher ranked fuedatories (aka the ones with the most political power/biggest states) are allowed three.
These are military restrictions to make sure the feudal lords don't ever have more military might than the Zhou King thus preventing a political coup. But...that leads to an interesting case when thinking about how Xianzhou's military is organized. (And don't think I didn't notice the "Zhou" pun...aka, 仙舟 could be a homophone for 先周, or "pre-Zhou" because...8000 years.)
If we assume the Marshal does in fact command all six fleets, then the Marshal essentially "owns" six "Corps" worth of military might, making them (her?) the "son of heaven" (天子). Thus, it's entirely possible each "general" actually serves as a feudatory prince to the Marshal. This is how we can explain why not every "general" is actually a military general. Especially since we apparently have confirmation that Zhuming fleet's general is an engineer.
Am I probably overthinking this really poorly structured arc? Yes. But also...I might be onto something...
Edit: OK, to address "but the fleet started with 9 ships"...
9 is a clear reference to the Imperial Number. This is a well known cultural reference that doesn't need explaining to any Chinese viewer. However, the writers decided to allow six ships to survive when there's only five Vidyadhara High Elders to assign to the ships. Why six ships and not five ships? What is the literary/historical context of "six"?
(OT: I hate the entire English translation decisions regarding Vidyadhara, will get into this in the future.)
Sure, it's possible the authors decided to throw a dart at a number wheel and it landed on six. It's possible they decided to go with the next multiple of three in line after 9 for some reason. But given that we only have one ship's worth of maps but we're given tons of information about other ships that we won't have access to for a long time, deciding to keep the Xianzhou fleet at six in current timeline is a deliberate decision. Also, given the many obscure historical references in the design of Luofu, Xianzhou, Jing Yuan, etc., I find it hard not to believe such an obvious reference to historical text isn't on the authors' minds when they were designing this area.
This is meant to be a metatextual analysis (see tag). I'm not merely trying to piece together the plot points based on lore. [/end edit]
Also, again, not sure how much of the bilibili wiki I can trust since this is the part that's un-sourced, the Cloud Knight ranks seem to be:
元帅、将军、骁卫、士兵、策士、司库
So, since the Marshall isn't on Luofu, that means Jing Yuan was basically second in command (at least of the Cloud Knights) until the death of General Teng Xiao. (Also, I realized reading the English wiki, 龙狂 got translated as "Dragon Delirium", which sounds so much less dangerous than it does in Chinese. 狂 is better translated as "psychotic rage" than "delirium". So what I'm trying to say is, in English, it sounds like Dan Feng was suffering from a heatstroke while in the Chinese version he's experiencing a murderous psychotic episode during the battle against Shuhu.) This really suggests Jing Yuan was very much an adult by the time of the Quintet era. I have a whole thesis on this I'll get to at some point.
Finally, just for my own reference, we apparently know the five dragon leaders (I can't take "High Elder" translation seriously, when the Chinese implies he's a KING) assigned to the fleets, and unsurprisingly the "unknown" fleet doesn't have a dragon:
天风君:曜青龙尊,掌应龙之传。宰制风雷,膺责守望胎动之月。
炎庭君:朱明龙尊,掌虬龙之传。炳辉天火,膺责守望太始燧皇。
冱渊君:方壶龙尊,掌蛟龙之传。驯驭冰涛,膺责守望方寸烟海。
昆冈君:玉阙龙尊,掌地龙之传。凝思静默,膺责守望息壤渊石。
饮月君:罗浮龙尊,掌苍龙之传。行云布雨,膺责守望不死建木。
Also, also, the dragons include all 7 elements, hohoho...
天风君 - Wind and Lightning
炎庭君 - Fire
冱渊君 - Ice
昆冈君 - Physical and Quantum (technically earth and quiet contemplation...but those aren't elements in the game so...)
and 饮月君 (our Imbibitor Lunae) - Imaginary (literally "moving clouds and arranging rain", which is a metaphor for controlling reality/creating illusions but is also a description of someone commanding the weather, or having immense political power...Chinese is layered and complicated OK?)
Let's see if I'm right as the game slowly releases all the dragon kings...