Hello! This is my first post on the Total War forums, but I feel like this idea is one thought of by many and will be received well if done right. I have read many threads and a big main point in why it shouldn't happen is because hardly anyone plays multiplayer compared to singleplayer in terms of statistics. This may very well be true, but I believe there are a few reasons as to why this may be.
I think a big reason in why multiplayer seems to not be as popular across all of the Total War titles ironically lies within the fact that there is simply a 2 player max for co-op campaigns. I am sure that there are many people with more than 1 friend that are fans of the Total War franchise and would utilise the multiplayer campaign feature only if they are able to play with each other in the same game without leaving anyone out. Because this isn't the reality, they most likely just don't even touch multiplayer at all and if they do, most likely not as much for the fact that not all of them can play. I have a big feeling that this will change if the player cap is raised, and we would see multiplayer start to get on par with singleplayer in terms of player count. Because of the 2 player limit though, I feel like this contributes to the stats of low multiplayer usage compared to singleplayer usage.
Another point is that not only will the usage of multiplayer increase, but in turn we will also see an increase in the consistency of the player base over the weeks and months after launch because it adds more re-playability.
Another point that is made as to why it wouldn't work is that the turn times would be too long. I don't see this as a problem as such because if you choose to go into a multiplayer campaign with more than 2 people, you should expect this to happen. It doesn't hurt to expand upon a feature in a way such as this as it isn't anything major such as a whole new diplomacy system for example. If you don't want long turn times but want to play with more than 2 people, then you can easily turn on the option that adds a time limit to each turn. This means that each turn will be a certain time at max, meaning the rounds will obviously go faster. Otherwise if you don't want to enable a time limit, then there is not much you can do as you can't really have it both ways as that's just not how Total War works.
A similar point which pinpoints the slowness of the game is that the battles are going to be the main thing to slow it down, as you could have a battle coming for each person in each turn potentially, making it take an hour easily to go into the next turn. I can see why this would be an issue and there isn't really a way to speed this up, but everyone can take part in battles regardless if it's head to head or normal co-op. With normal co-op, you are able to gift units to your co-op partner. This means that both of you can play the battle and help each other out. Sure this can make the game too easy but it exists, and in past experience I find it already becomes much less boring even if I'm given a single catapult unit, because you can just press insert on your keyboard and fire away. However, head to head campaigns would work MUCH MUCH better with this, because you are able to play as the AI (as long as you are not allied with your co-op partner(s) of course, but I think an option to turn this off would be nice as I mean, what's the harm in letting people play as the AI against their friend while their faction is allied with their friend? It's a head to head campaign, not a normal co-op campaign where you both achieve the final goal together. You are meant to fight each other eventually in this mode so it just adds a fun factor.) With multiple people, you could (just from the top of my head) choose if you want to play as the AI or spectate (basically you would be able to be gifted units by the player) which creates for some really fun scenarios that can potentially recreate the feeling of multiplayer custom battles. For example, if there were 2 AI armies attacking 1 player army and you were playing with 4 people, 2 people could play as AI, using one army each respectively while the other spectates and is gifted units by the 1 player defending. This means that each battle can be a real challenge, unless of course all 4 players choose to be on the same side. But then that's just their choice and just means they chose to make it an easier battle this time.
The last point is basically just a mixture of multiple misc points related to UI and the development of the multiplayer aspect. These don't necessarily point to a reasoning why co-op with more than 2 people don't work, but they can be the things that make multiplayer less played which in turn can damage the later development of multiplayer if the devs feel like they are wasting their time on it.
There are problems with multiplayer such as de-sync as the biggest one (however, I feel like I am not experiencing this as much in later titles compared to earlier titles. I don't know if that is just me but I feel like its going down the right path), lacklustre in-game text and voice chat system (I think it would be a nice touch if this was fixed but I don't feel like its a massive priority because you can easily use third party programs like Discord or Teamspeak for example to speak. But again I know people play co-op campaigns with strangers), non-compatible game version error (usually caused by not having matching mods, so a feature where you can see which mods are installed from the Steam Workshop for each lobby would be nice so people don't have to mess around for hours on end trying to send mods to each other to match them up).
There may be others but I feel like these are the biggest ones I can think of right now. If there are any others please tell me down below. However, I feel that if more work was put into multiplayer, these can be easily fixed and then multiplayer will already be halfway there to perfect in my opinion. To make it completely perfect, adding in more than 2 players available for co-op (can even be 4 player max and the majority of people wanting this, including myself would be satisfied and I think 4 players is a good middle ground to stop it there. You could go up to 8 players as a max for the full what would be a 4v4 if it was a multiplayer custom match, but that would be way too much in my opinion. But again, if its possible and able to be done, I'm sure people would enjoy that as well. Personally, I think 4 players max would be good to have with the least issues) will be great, and I think that we will see a big influx of people playing multiplayer and a higher consistency of the player base staying weeks and months after launch. And most importantly, the game will have even more replay value and become a lot more extremely fun than Total Wars usually are.
Lastly, sorry if I missed anything out as I sorta just wrote this based off of what was from the top of my head and wanted to post this in case it brought up any ideas that could make this possible for Three Kingdoms. I feel like the game will grow to be a bigger franchise if they focus on aspects like this without taking away from other aspects like single player of course and also the future games of the franchise as well. For me personally, the Three Kingdoms period is one of my favourite periods, as I first discovered it from a PS2 game called "Dynasty Warriors 2" and had a lot of fun playing it and always wanted a Total War game that was about the era. I also have a lot of friends who are interested in this era and would be stoked if we would all be able to play together like I am sure many, many other people out there would be as well. Now this game is becoming a reality, I really want to share these ideas that can potentially make it even better than it can be. Thanks for reading this really long post, please give me your thoughts below!
TL;DR (although I'd highly recommend reading all of it to avoid misinterpretations, especially as I am not the best summariser and these should just be used as a quick reference for an idea of what I mean, especially if you are choosing to reply to some of these points IMO)
1st point - Low stats of multiplayer compared to singleplayer is potentially caused because of the development of multiplayer and that it has 2 players max only.
2nd point - Turn times being too long isn't necessarily a problem because you should expect this if you want to play with more than 2 people. You can easily enable a time limit for each turn anyway. If you don't like playing with more than 1 person in multiplayer, then just stick to that as it doesn't hurt to add in an extra option that many others will enjoy.
3rd point - Battles making turns take ages can be understandable, but won't exactly be boring because of spectating and then gifting units, and playing as the AI (it's kind of hard for me to explain it in few words here as I always struggle with that, so I recommend reading that one, especially as I mention some ideas that would, in my opinion, make it less restrictive).
4th point - Most if not all of these issues surrounding multiplayer can most likely be fixed easily if more resources are put into it. Fixing these and then allowing more people in a game will make it perfect and increase the consistency of the player base, the "fun level" of the game and more replay value.