Some added content for the 17th and 18th centuries would be most welcome.
... But it does feel like the focus has changed a bit when all the new building upgrades we got were researchable before the first third of the game comes to pass.
Well, people hardly play the endgame at all. About a month ago I reported the bug that after 1740 ronin rebels start popping up all over Europe. This was a really obvious, in-your-face bug IF you're playing after 1740 (it's been fixed in the latest patch). But I was apparently the first person to report it. I have to conclude that people hardly play the period after 1740 at all.
That the new buildings are all researchable in the first third of the game is purely the devs' design decision. Nothing about the game starting in 1399 made that decision necessary. As far as I can tell, the new buildings were designed purely with multiplayer in mind.
This thread isn't meant to just be about the Byzantines and how the Ottomans collapse.
It did become about that, though.
But the problem (of the late game not being well developed) is not because of the Byzantines. The systems that the developers have spent a ton of time on, reworking them seemingly every expansion, are the HRE, the Papacy, and the Hordes. Those are the systems that require not just some scripting but reworking the .exe. And, it's not because the devs have spent so much time on these things that they couldn't improve other places. For instance, the single change that I've found improves the historical accuracy of the game most is making Shamanic religion non-annexible. With Shamanic religion annexable, the Europeans settle as far as the Mississippi by 1550: with it non-annexable, the North American tribes normally survive to the end of the game, as they did historically. This a really obvious change to make if you care at all about historical accuracy in North America, there's no down side to the change at all, and it requires deleting or commenting out one line of code. I have to conclude that the devs don't work on North America because they just don't care. The HRE is interesting to them, the colonization of North America is not. Similarly, the devs made the Incas into a "Tribal Democracy", because the alternatives were (1) to make them tribal monarchies that had to invade their neighbours or get penalized, (2) to make them non-"tribal", and everyone knows that that would be totally unrealistic as no natives in the Americas could
possibly be as well-organized as Europeans, or (3) to spend 15 minutes to half an hour writing up a new government type that's tribal, a monarchy, and doesn't have to constantly invade its neighbours. But again, I have to conclude that the devs just don't care about the Americas, or anything outside of Europe and Japan, really. Which is unfortunate.
The problem is that people don't usually play into the late game, and the reason people don't do that is that countries get easier to play as they get bigger. So once you're country reaches a certain size, you've basically won - you can do anything you like and there's not much the AI can do to oppose you - and that's not a challenge, so most people stop playing there. So IMO the solution is to make larger countries harder to run, so that the game will remain challenging longer, so people will continue playing further into the game, so there will be more demand for late-game features.
If you really want to make the late game better, then I'd make two main changes. At the moment, the only real disadvantage for being big is that your stability costs go up, and that's nowhere near enough to compensate for all the advantages. Even the AI gets more stable when it gets bigger. (The building system isn't a disadvantage to large size, it just reduces the advantages of large size, mainly for large AI's which don't know how to prioritize their building construction: if you're a player, no you can't put a temple in every province, but how much does that actually matter? SO the new building system makes it
easier to be a huge empire in single-player.) Rebellions need to be made more coordinated, some events need to scale with the country's size (e.g. the event that sometimes gives you a rebellion when you centralize gives you one rebel stack whether you own one province or five hundred provinces - it shouldn't be
easier to centralize when you're big!), big nations need to have some more interesting events, the AI should gang up on countries which get too much larger than any other country, etc.
Secondly, flatten the \common\technologies\land.txt some. As it's written, the effectiveness of your troops is proportional to the cube of your land tech, because land tech gives you improved troop types, better stats like infantry_shock which multiply how much damage you do, and better stats like military_tactics which divide how much damage you take (and which the AI doesn't know how to use, *cough cough*). Those things are multiplied together, making European armies more technologically dominant in the 1500's than they historically were during the Victorian era. Where's the fun of colonizing in India when you know your army will annihilate an army 5 times its size at the cost of 25 men? With the vanilla land table, all that matters in determining a battle's result is land tech, land tech, and land tech, but I've played games with a flattened land table, and land tech is certainly one, important, factor, but things like army size, skill of generals, and terrain also matter. You can beat the locals if you give your colonial armies the resources they need, but take your victory over the locals for granted and you'll find your colonial army dead. I lost an army to the Maoris once (i.e. NAT), in the 1700's, which is exactly the sort of thing that happened historically from time to time. It keeps the expanding-outside-of-Europe subgame interesting, and it's realistic, what's not to like?
Make the game stay challenging when a player has become a large country and more people will continue playing further into the game and there'll be more demand for late-game features.