I finished a Deity Modern Age Advanced Start game last night and I feel like it gave me some insight into this topic. Some relevant notes:
- Modern Age lasted to about 120 turns or 80% age progression
- AIs adopted ideologies shortly after me despite rushing for it
- AIs pursued the Space Race legacy path competitively with most getting to 2/3 before I reached victory
- AIs utilized tier 3 modern Age land and naval units wars, aerodromes were present but not utilized for war
- Influence and Gold currencies were much more precious due to scarcity compared to cost
Some conclusions I made from my game is that 1) the Modern Age in a full game lacks a setup phase like Antiquity (founding your civ) and Exploration (getting to Distant Lands) which makes the victory race much more prevalent, 2) despite being paced better, tech still felt funneled into Space Race and I ended up with all masteries rather than having to choose to specialize, and 3) Influence and Gold are even more important than they were in previous ages and I had to be careful with how I choose to use it compared to my full playthroughs. Playing Modern Age just by itself definitely feels more complete, but my conclusions only reinforce my belief that the Modern Age should be extended rather than a 4th Age added.
I agree that advanced start modern age is pretty good. I guess you can either argue that production/gold at advanced start tend to be low enough to create an artificial constraint, or that it's proof the snowball is too much.
I don't think I get a clear picture of "victory-only 4th age":
1. Does 3rd age keeps its legacy paths or they are redesigned?
2. What should be included in 4th age victory race?
3. Which game mechanics should be available in the 4th age?
4. What civs should be used in this 4th age and with which abilities?
I think we're approaching this from two different viewpoints, with different priorities.
My priority is making victory feel more satisfying. I think that there's a fundamental issue with having a normal gameplay loop in an age where you are racing to victory. I.e. the standard gameplay loop and the victory race are in opposition to one another. In a victory race, the goal - especially on higher difficulty or in multiplayer - will be to doggedly pursue your chosen victory type. That means you won't really explore the features of your chosen civ unless they help boost the way you are trying to win. That in turn skews the designs of those civs if they are to be relevant. The snowball also gets pretty extreme, and adds to the feeling that your chosen civ seems to really not matter. Making modern era work like other eras - where you are trying to score points rather than a race I think is a good idea, and would really help let those civs shine. But, score victory probably isn't very satisfying for a lot of players, it is kind of an "oh, the game ended" kind of moment.
To that extent the idea of a short 4th "victory race" age, which doesn't try to introduce new civs, and which just pools together the accumulated bonuses you've acquired, feels like an interesting way to make an ending actually feels definitive. At the same time, it allows the current modern era civs to go through a full game loop. What I really wouldn't like in a 4th age is for Firaxis to just shift the problems which are currently there in the 3rd age, one step further along the chain. That would to my mind devalue any new civs who were introduced.
I get the impression that your priority would be a full age where we'd get to experience cold war/globalization/WW2 etc, with a roster of contemporary civs? So I can appreciate that a short "victory age" would feel like you were being cheated out of something cool.
That's perfectly valid, but to me, just adding an age without solving existing problems still leaves the question of how to make victory satisfying still up in the air. It still leaves questions around how to make civs matter in an age which is a victory race, how to mitigate a 3rd snowball cycle when 2 is already a lot, and - for me - the micromanagement at the end of age 3 is approaching the limit of what I want to see, how to keep that under control? Plus, the civ roster already feels very sparse and repetitive with only 11 civs per age, I really don't want to see a new age's worth of civs until we've at least doubled the current civ count.
And I guess you could always combine the two viewpoints and have a 5th mini-victory age after the modern era (or an era of your choice).