As someone who isn't very interested in Warhammer, (but bought it anyway for the lack of anything better) I wanted to sit down and think about all the features I'd like to see in a future historical title.
Please feel free to add if I've forgotten anything or improve on the ideas.~
1. Complete modability - I'm talking about Medieval 2 levels of modding here. It would only increase the longevity of the game, and allow for creative improvements on the game that the devs hadn't thought of before. It doesn't affect the sales of the DLCs or the next title as people will still buy the DLCs that CA makes if they're good quality, but preventing the community from making any worthwhile mods by limiting the tools they're able to use just so they can sell lackluster faction DLCs is just distasteful. (More on the DLCs at the bottom)
2. Better Diplomacy - Believe it or not, this is a huge part of the "strategy" aspect of Total War. I know that the name of the franchise is the complete opposite of this feature, but without diplomacy, the game becomes "survive x amount of waves of enemies". I'd like to form stable alliances that last throughout a campaign. I'd like factions to want to form deals with me when I'm superior than them, NOT lose relations with me because I'm a "great power." It's unfortunate that you named this franchise "Total War" but most people who play it don't actually want to conquer the whole map. They're here for the journey, not the destination. Fewer diplomatic options means a less fun journey, more hacking and slashing.
Also... MAKE TRADING SETTLEMENTS A THING AGAIN.
3. Remove the building slot system - It's not realistic and becomes extremely repetitive after a while. In Warhammer, you only need 2 regions at most to build every possible building. (Also makes conquering new regions redundant except for the heck of it) Real cities always keep growing as their populations increase, and you get to build more buildings. There aren't "maximum building slots". Make a wide selection of buildings available, but only once you reach a certain population level, like Medieval 2.
4. Roads & Trade Routes - Having roads in previous titles allowed us to visually see our lands prosper, and let us or our enemies to take advantage of them and attack their/our trade routes. This was a MUCH better way of "raiding" than what is in Warhammer. You shouldn't be able to raid a province by camping in a corner at the edge of it.
5. Strategic Campaign Map - Nowadays, there's almost no value to conquer a region strategically other than its' potential resources. You can't create choke points. This makes the strategy incredibly bland. Some of the most epic stories are about creating chokepoints for the superior enemy, like the 300.
If any of you has played Third Age Total War, I'm sure you agree that playing as Mordor and having both Minas Morgul and The Black Gate blocking passage into Mordor was awesome. As was protecting Cair Andros and Osgiliath to prevent Mordor from crossing the Anduin. The stakes were high, those locations mattered.
6. Make the AI smarter - Instead of giving public order, diplomacy and financial penalties to the player (looking at you, "great power" -.-) and giving buffs to the AI.. You could make them smarter? If the public order is low, make them build stuff that help that, or garrison an army there. Or give them enough sense to not declare war on me from the other side of the world. I know the game is called Total War but it doesn't have to be all about war. It IS a strategy game after all. The AI throwing stacks of armies at me constantly isn't exactly strategy.
7. No more generic cities - I'm sure you could spend the fraction of the DLC money you're making to hand-craft the cities in your AAA game. I don't want to fight the same battle on the same map throughout the campaign. Let me recognize the different cities each time I get to fight in them.
8. REAL traits/items - I love the addition of small RPG elements into Warhammer, with the exception of one detail.. they serve only as stat buffs. I'd like traits like "coward" that makes the leader flee at the slightest hint of defeat and gives a huge morale debuff to his soldiers, or one with the trait "brave" that keeps on fighting against all odds and inspires the soldiers under his command - as opposed to traits that just.. give +5 armor.
Same goes for weapons and armor. Instead of giving whatever buffs, make it so that plate armor for example, makes them immune to arrows while giving penalties in speed.
Also.. MAKE THE ARMOR/WEAPON VISIBLE ON THE CHARACTER.
Now that would be amazing.
9. Family Tree - One thing that made my Medieval 2 campaigns memorable was starting with a certain king and eventually getting one of his sons to inherit his titles and legacy, accomplishing more deeds in his father's name. Sure, the game had flaws, like adding every new general to the family tree or not being able to pick your heir, but it was way more fun than what's in the more recent titles. Attila kept the system to a degree, which was nice, but it was still lacking.
10. Agents & Captains - Creating a new leader to control more armies seperately sucks, let's be honest. And having multiple types of agents that basically do the same thing does too. The best way to solve both these problems is to turn agents into "captains" that can command half the size of an army that leaders can, but also get to perform agent actions. You could recruit captains depending on their weapons (ranged, melee, cav etcetera) or traits. I'm betting this would stop the AI from agent-spamming too, as the captains would have better uses elsewhere. Also... GET RID OF GARRISONS, THEY'RE ONLY THERE BECAUSE OF THE INCOMPETENT AI.
11. Better DLC - Please, CA, stop ripping factions off of the campaign and selling them for money. That is not optional DLC, that's selling an incomplete game to sell the rest of it for extra money. That's like Domino's giving me 75% of a pizza and selling the rest of it for more money, slice by slice. Instead of taking from the game, you could build upon it by adding more units, buildings, traits, and items to all factions. You would profit just as much as you do now, and both you and your fans would benefit from it.
Anyway, thanks for reading this super long post. Insert a potato picture here.