Your versions!

[Cao Ah Man]

You're the director in charge of character portrayal in the next Dynasty Warriors game.

How would you do it? Who would you change? What character traits would you give them, how would you alter how they've been done so far?

[LordSimaYi]

Make Wei Yan more 'Normal', Jia Xu look older and to not add Sun Quan and Shang Xiang in the early Wu missions where they are both less than 10 years old.

[DragonAtma]

Where appropriate (i.e. any officer that's active for 10+ years), I'd give officers two or three faces (young, middle-aged, old) and use them as necessary. Seeing Sun Jian with white hair when he's in his thirties is just silly, and so is seeing Liu Bei look the same in 184 and 221.

[Dong Zhou]

Beg the story go to go back to one per battle and have a long talk about how to juggle the roster.

Work on Xiao Qiao where I can see the basic idea but the execution is annoying, make Guan Yu more human (including how Guan children react to him), alter Wei Yan, change Sun Quan to his more entertaining historical personality, tone Zhang He down a bit. The ageing character models would be nice

[Zafar Khan]

Highlighting the criminally underrated general like Lü Fan whose achievements were robbed by Zhou Yu in fictional and modern versions.

basically to reversed the policy of "take away the great achievements of the less handsome Lü Fan and give it to the very handsome Zhou Yu"

[Rydain]

Give Cao Ren his DW4/DW5 era friendly face, teardrop war paint, and self-sacrificial insistence on forging a sense of do least harm ethics within the necessary evil of war. He also needs a strong supporting role in Wei's story and a powerful presence in his iconic battles, commensurate with his historical defensive prowess and importance as commander in chief. Cao Ren went from one of the series' deepest characters - with a uniquely cohesive archetype amplifying his internal conflict - to blandly loyal shield schtick. The newer games can't even be bothered to highlight his rescue at Jiangling, which had its first and only portrayal in DW4:XL. At least he finally has his shield once again, a critical part of that archetype I mentioned.

I also want loudmouth roughneck Xiahou Yuan back. He might have more respect now, but he largely boils down to Easygoing Badass Archer Important to Cao Cao. With his casual self-deprecation, insistence on staying positive, and interactions with women that could be either chivalrous or condescending depending on how one read them, his DW5 era self had more distinction from others cut from similar cloth. Xiahou Yuan can keep his comparatively slimmed-down looks, though.

[Shen Ai]

Redo Wei Yan completely. Overhaul him entirely.

Scrap Cao Pi and replace him with Cao Rui. Ditch Zhenji for Lady Bian.

Add in Cao Zhen and expand on the Northern Campaigns for Wei story mode.

Revamp Sun Quan's entire character. Get a new voice actor, make him more like he was in the 2010 drama.
Give Zhou Yu his sword back.

Humanize Guan Yu. Get rid of Guan Suo and Bao Sanniang and Gua Yinping. Add Liao Hua and Wang Ping.

For Jin... not much I can say. Maybe put more of the focus back on Sima Zhao being the unlikely inheritor/conqueror.

Do a similar kind of hypothetical story mode, but this time do it for factions of characters as opposed to just the whole faction (example, Cao Cao, Xiahou Dun, XIahou Yuan, Dian Wei, Xu Chu, and Xu Huang share one mode, while Cao Rui, Cao Zhen, Sima Yi etc. share the other).

[Sun Fin]

Highlighting the criminally underrated general like Lü Fan whose achievements were robbed by Zhou Yu in fictional and modern versions.

basically to reversed the policy of "take away the great achievements of the less handsome Lü Fan and give it to the very handsome Zhou Yu"

All up with this, without doubt Lu Fan is the most underrated officer of the era. But to be fair to Zhou Yu he loses out in the novel/games because as you say he gets given Lu Fan's achievements but that means he turns from a top tier general to a strategist. Not that there's anything wrong with being a strategist but that wasn't who he was historically.

[Shen Ai]

Probably because Zhou Yu was a bigger player than Lu Fan politically and in the military. Zhou Yu was the Grand Commander, was he not? And the novel does the same, extracting the achievements of various generals and bestowing them on Zhou Yu. Though Zhou Yu himself was the field commander to many major victories, so to say his achievements were not his own isn't fair.

Koei has also started to portray him back to a general figure again. His #8 outfit reflects this. Half armour, half robe.

[Sun Fin]

Probably because Zhou Yu was a bigger player than Lu Fan politically and in the military. Zhou Yu was the Grand Commander, was he not? And the novel does the same, extracting the achievements of various generals and bestowing them on Zhou Yu. Though Zhou Yu himself was the field commander to many major victories, so to say his achievements were not his own isn't fair.

Koei has also started to portray him back to a general figure again. His #8 outfit reflects this. Half armour, half robe.

Lu Fan was briefly commander-in-chief as well I believe. Possibly between Lu Su and Lu Meng?

However you're right that Zhou Yu was a bigger name but that was partly because Lu Fan was incredibly humble - at one point in time he took a role far lower than his rank demanded to sort out an admin problem. Yet he joined Sun Ce right at the beginning with his 100 retainers and was Ce's primary adviser for all things military. Zhou Yu may have been Ce's best friend but that translated in to being his most trusted general. Hence why he led the rear guard during the Wu campaign and commanded the army that held the border against Huang Zu rather than his adviser. I see no reason why there isn't space for both adviser and General in a DW games.