If you were exhausted by reading my post, think how exhausted I was by writing it.
So, just a few quick reactions to some of your reactions:
Just saying that how Civ looks at history should change doesn't really mean a whole lot. What does that actually mean for gameplay?
Guilty as charged.

That's because I was only interested in showing that there are two general ways you can go about making revisions:
1.
Modify and tweak the existing game. Advantage: Most of the structure and elements can remain, which makes it easier to imagine how gameplay might work out. Disadvantage: You'll probably just end up gilding the lily. That's the problem that dh_epic worries about.
2.
Rip it out and start over. Advantage: Lily-gilding won't be a problem, because there will be no initial lily to gild. Disadvantage: Very hard to imagine how gameplay will work, since you have to imagine everything from scratch.
I did not mean to make a concrete proposal by bringing up Toynbee. I brought all that up only so people could see a concrete example of how you'd
start working under option 2.
The problem with this sort of approach is that it challenges the historical basis for the game, rather than the underlying gameplay mechanics.
Well, yes. That's because if you only concentrate on the existing mechanics you will risk making changes that don't really work. There is a strong likelihood that they would be minor or tedious changes (of the sort that dh_edit decries in the first post of this thread), or that they would be conceptually flawed additions (like "dark ages," which would frustrate the fundamental "flow" of the game). But if you reimagine the historical basis, you might be able to save most of what is already good in the game while finding ways of adding new and fun stuff. The result, doubtless, would
not be an "improved" version of
Civilization, but it could be fun "complement" to the original.
Regarding my example, ChrTh in various posts writes:
The gameplay (and the initial victory conditions of Conquest and Space Race) are predicated on this notion. If the ultimate goal is not to do so ... is it even Civilization any more? Does this statement need to be the essential anchor for any discussion on future versions of the game? If so, many of Mxzs' ideas may not be suitable for a Civilization game.
...
There's a huge difference, though, between the complexity of a game like Tetris (or Pacman, or Space Invaders) and a game like Civilization. In the former type of games, because the complexity is so low, people are more willing to accept eventual defeat. In the end, all you put into it is time and since the results occur throughout the game you gain 'internal happiness' throughout play (woohoo, I nailed 4 rows!). In Civilization, however, there's so much complexity involved (economics, fighting, research--no matter how it occurs, etc.) that there has to be a positive end-result. Otherwise there just isn't enough of a payoff to justify playing the game. And as someone who has lost a lot of games towards the end, it's exceedingly frustrating. The idea that the game is lost at the end no matter what you do, yikes, I just don't think there's enough masochists in the gaming community.
I admit that I do kind of like the "proposal" that I used for an example; I've been mulling ideas for
Civilization changes off and on for over a year now, and this is one that I keep coming back to. Still, you make points that might stop any Civ developer in his tracks. Civ's current framework is so well-known and successful that
anyone would be reluctant to mess with it. You would only know my revision was "fun" after building and testing it.
That being said, I don't see it as a theoretical impossibility. "Tetris" holds many lessons beyond "it's an addictive but unwinnable game." You mention moments of "internal happiness." I think my example-- Look, can I just call it ATC ("Arnold Toynbee's
Civilization")? Okay, I think ATC could have a similar feel. The game would have to be designed so that its "flow" gave you moments of respite and success. But those moments gain their sweetness in proportion to the horrible tension of the moments that precede them: the best moments in "Tetris" are the ones where you've almost lost but stage a comeback. Similarly, an ATC game would have to be built so that it "pulsed" with moments of crisis and victory. I suspect such a game would feel a lot like the Avalon Hill board game, which has been well described as "an extended exercise in crisis management."
It might also be possible to add in something like a "winning" end-state, even to the extent of putting the original Victory Conditions (dominance or space travel) back in. Toynbee notes that new civilizations arise on the ruins of the old ones, often taking over bits and pieces of their inheritances. So, ATC could be structured like a campaign game. Each episode of civilization management ends in collapse and disintegration, but then you start afresh with new "settlers" who are wandering around in the world as it was the moment your old civilization collapsed. (In other words, once Rome disintegrates, you take over the Franks and start trying to build Western Christendom.) Much is always lost in these dark ages, but no one ever starts from zero, and over the campaign you might be able to work your way up to modern civilization. In fact, collapse and disintegration might become tools you would have to use in order to get yourself out of a cul-de-sac.
(Example: You accidentally wind up re-creating ancient Egypt; thousands of years of pyramid building stretch before you, with no hope of ever actually getting to the moon. So you let the Arabs in; they efface everything; you lose most of your tech; and you basically start over with your traumatized population, this time avoiding the mistakes that had turned your old civilization into a mortuary culture.)
* * * * *
Final note on ChrTh's posts: I think the tech tree idea you advance is
very intriguing and much more fertile than my idle noodlings. I might be back with more comments on it, but it sounds to me like it has real possibilities.