What is your final version for your faction?
As someone playing mainly order factions, over the course of Total War Warhammer, i have become a fan of not only that faction but also the lore. Naturally one always wishes for more mechanics to represent the favourite lord or hero better or even the favoured nation.
In my case i would really love a knight mechanic for the empire with the addition of Kurt Helborg, together with Grandmasters or duelist characters that dont instantly get folded like empire captains (Franz needs Ludwig Schwarzhelm) and more interesting skill trees for legendary lords.
I would also love "cheap" legendary lords for Balthasar Gelt in the form of wizard lords for the collages of magic so he has a return besides items, after investing in the different orders (since i feel like the system is very shallow compared to other factions) and in this the addition of wizard lords and potentially ( a man can hope) the addition of Max Schreiber.
Lastly, to bring the empire up to date with warhammer 3, army abilities with prayers should come into play. Currently as Emperor once get a very slight mechanic of balancing the interests of the different elector counts. But overall, you cannot play the campaign of "embracing" Middenland and thus recieving massive amounts of Knights of the White Wolf or bonuses to meele troubes. The State Troops are also not a massive upgrade over regular ones (especially the knight variants). Thus i would love to see this fleshed out to add replayability and certain traits only some provinces provide, making keeping them alive and well a priority and truly granting their form of combat massive buffs (similar to how it would work in the real world, grant a province unlimited money and it prospers - until it feels to strong and starts warring on its neighbours, or you).
Lastly there are lords that are really left out. We have Boris Todbringer as representation of Urlic. But the representation of Sigmar does not really have a Sigmar oriented campaign at all. A believe system similar to the kislev one might work, where the Empire in general can invest in all major gods, such as Taal for Hunters, Ulric for war, Sigmar overall, Shalliah and Mor. We have good representatives for almost all of them, granting them bonuses for investing in their gods. Volkmar for Sigmar (and more army wide buffs and prayers, because buffing flagellants alones is really a poor buff in my opinion), Elsbeth for Morr, Markus Wulfhart for Taal and Toddy for Ulric. And Franz has to balance between each of them, getting no bonuses for devotion for a single one and potentially incapable of easily reaching the highest prayer abilities.
TLDR: I have presented my vision for a final version of the Empire in Total War Warhammer 3. And i am super interested in the final version that YOU might have for Chaos, Elves, Dark Elves, Dwarves etc.