Wait, do I understand you correctly? You mod the game by changing a few key values like research rate, growth and unit production?
And then you complain about the AI because they can't handle your changes to the game code?
Maybe you should look for a more professional mod that adds a slower game speed than marathon.
Talking about balance while using any kind of mod can be quite confusing in a general discussion forum :/
Not exactly. The modifcations to the values just exaggerate a flaw in the AI. The flaw is there without any modification - it's just more noticeable with it. When the game pace is Standard or faster, you hardly pay attention to the fact the AI is running negative GPT or over-expanding because research is happening fast enough they can snag different luxuries or build economy-related building to compensate but they fact they are always over-extending their resources - despite bonuses at higher difficulties - is a basic flaw. On Epic and Marathon they reduce the pace of construction to compensate for slower research so the AI doesn't over-extend for too long of periods, but it's still noticeable. As for "professional mods", my attempts to glean assistance on the forums years ago and the lack of other mods out there pretty much prove few have an interest in my style of play so that is not an alternative, so I'm stuck with what little I can accomplish by studying the files and testing adjustments.
I can understand and expect a large military build-up leading to a DoW or in response to one (and by that is likely the logic the AI uses since it's seems to declare wars every 5 turns or so on someone only to sue for peace against that target 10 turns later after it's started two more with other targets), but not trying to consistently field a military larger than Support or GPT can tolerate. The same for Happiness, it's understandable to drop low in Happiness to grab a new luxury or a necessary strategic resource you can utilize now but not to churn out a settlers constantly to form an ICS just because you aren't at -10 Happiness yet.
And I don't merely change a "few key values" I do my own mods, usually major overhauls, and often incorporate others - mainly CivUP and VEM. The issue is, I don't want slow unit/building production with slow research. I don't want a game that's just clicking Next Turn for long periods of time but I don't want to be racing through techs either. I'd like to field a unit and see it in combat for a while before it's obsolete; however, despite my extensive searching of XML and LUA files I can't seem to find the necessary adjustments to make to the AI to make them understand the mechanics because most of that behavior is core to the game.
For example, to further slow down the game I once reduced the science per population to 0 (because it wouldn't accept anything but an integer - I'd have been happy with 0.5 or 0.25 but it was choice between 0 or 1), but gave the capital building a +50% per pop adjustment (as well as reducing other bonuses - core values of buildings, bonus per pop from libraries and public schools, modified universities to give 1 per jungle but also 1 per sea resource, marsh, and ice tile, reduced bonuses from wonders but allowed nearby universities to restore them to original levels, modified korea's bonuses to specialists - removing it entirely from generic Citizens - etc.).
Playing in Hotseat the pace was perfect for me, yet adding in AI, I failed to find any settings to tweak to adjust the expansionist zerg all AIs (including Ghandi) use. Sure there are values for flavor of things like Settlers or having sufficient military units but those values didn't seem to have any impact. The AI wanted to research faster, so it's response was to churn out settlers like crazy to build more cities... which didn't help squat pre-library since all research was done by the capital and the act of training settlers stopped the growth of the capital, which slowed research more. I never trained settlers, I bought them outright (even though they cost close to 2000 each) with the funds I made from having a positive GPT and stomping barbarian camps.
My army always stays under Support levels with room to spare for workers, settlers, etc. Sure, I might lose units and even a few cities when, say, Germany and Russia both attack me at once because they 'Covet lands I possess', but I'll get them back easily since I have a stable economy and happiness and they don't. I can purchase units quickly to compensate because I have a balance in the treasury and my units suffer less damage because they've got a -33% from unhappiness... and they sacrifice units or waste promotions on full heal while I do fighting withdrawals or rotate units out to heal so I can spend my valuable promotions on permanent boosts.
AI combat tactics aside (because I know they're hard to code), they give us the ability to mod values but not the means to make the AI properly notice those mods... not to mention it appears the AI doesn't seem to factor current GPT or Happiness into its decisions in the first place. I'm not griping the AI can't handle my changes as much as I'm griping the AI can't manage an empire period. Play enough games without any modification and you'll see what I mean if you look, they added in ratings you have to juggle to keep an empire running and didn't factor them in to AI decisions.
This said, I did notice when I made it where Marshes (undrained) gave science with universities, I noticed the AI would leave them undrained (perhaps with a trading post) instead of replacing them with farms because it could detect they would possess value at the appropriate tech. I'm amazed, truly amazed, they put so sophisticated a system in where the AI would plan ahead so well based on a change I did to a building (with no other modification to AI settings) yet have the AI completely ignore such a basic part of the game such as keeping GPT and Happiness positive.
That said, I don't wish to derail this thread further from the OPs complaint of waiting so long for spies. I merely wished to point out that I, also, consider Renaissance to be late game based upon my playstyle. Although unlike the OP, I have no issue with spies being Renaissance... I'm just hoping the AI mechanics (or at least the parts I can adjust) improve with G&K to a point where my Renaissance becomes mid-game for me again...