I've thought about it, and 10 size 20 cities on emperor...it seems like you would need a good chunk of land for one, so with that in mind I started a game.
Note that I use legendary start - It obviously skews things in favor of the player on the higher difficulties - but the way I see it, this thread is about having fun with a civ-building strategy, so that's ok. It shouldn't be a cakewalk, you should be challenged, and you shouldn't use in-game exploits...but so long as this is reasonably satisfied, different settings are a-go.
Like I mentioned, I think having a cheap but effective military will really help with this strategy, since you can secure a large empire with very few units. Of course, an intrinsic part of the strategy is that there must be a dense infrastructure too...so you should have something that helps with the maintenence costs.
Enter china. Their Ub is not only a library, it also provides 4 gold. Sure, it costs 1 gold in maintenence, but the 4 gold grows with the economy buildings into a late game average of probably 6 gold per city. So I've got at least an extra 60 gold a turn you can pour into building maintenence.
A city tile itself will pay for the paper maker, a coloseum, and an entire theatre with just a bank and a market.... That's pretty good!
A size 20 Chinese city will, from the UB and the economy building modifiers alone pay for a stadium, and 4/5th of a theatre ~ 6-7 happiness.
Compare with Ghandi: A size 20 city will get 8 happiness from ghandi's ability.
But I digress.
Here's where I'm at on turn 83:
I just barely managed to overpower the iroquis. I basically beelined ironworking to get a heroic epic in the capital. As soon as the epic was up, I settled on iron right next to hiawatha, upgraded a warrior, and purchased a warrior which I then upgraded. My starting warrior turned into a spearman in a hut.
I clashed with hiawatha, stealing a worker that was hooking up his only iron before it was done. I'm clearly not a great civ-player - a clever archer usage let hiawatha (how did this AI manage to pull _that_ off?!) pushed all my guys back, but not till I had fought enough to spawn a great general. I snuck him up past a barbarian encampment through the city states, I took the honor tree and grabbed the promotion that boosts units when they have other guys next to them, and then I stomped all over hiawatha. In hindsight the GG was enough to, well, GG hiawatha, so that was dumb, but the game is only on emperor...There's probably room for a few errors here and there.
Now don't get me wrong; this game won't be about military conquest. But it should be plain to see for everybody that there's not a lot of room, and 10 big cities take up a _lot_ of space. Additionally, I really wanted to seize at least _one_ extra capital in addition to my starting one, to secure additional luxuries from the legendary start setting.
With hiawatha's capital down, I've secured the nothern land-corridor firmly enough (I only kept the capital, burned the rest). The western corridor is insanely slim...once I have a fort set up, nothings gonna get through; and if it does, that means I'm under attack, which means I get an extra great general soon, which means I can plonk down a citadel.
In other words, I've provided military security for my coming empire...now I need to plan it out. Figure out some sort of plan so I know what i need to do to get my empire where it needs to be.
That's more tricky than I would like. I have access to 6 disparate luxuries once I get calandar; butter up the right maritime city state, and I get dyes....so that's 35 happiness. Then there's the surplus resources: If I can sell silver and other resources I have a ton of, to more than 1 empire now, post patch, I can hawk a total of 12 surplus resources. Ideally, this would translate into the remaining 8 luxuries, but I'll be lucky if I can get half that. Either way, the most I can hope to attain by bribing city states and trading with other empires is an additional 40 happiness.
The difficulty level gives me 9 happiness, and the natural wonders give me at most 7. That's 91 happiness, and I need at least 210.
Building a theatre, a coloseum, and a stadium in each city, I get another 120 happiness, bringing me to 211...so it _can_ be done with buildings and trade alone, but that's a nasty 14 gold per city.
But what alternatives do i even have? smaller happiness-surplus cities could probably carry me some of the way, but I'm not sure any other approach will even make a dent.
And if it's going to be little happiness boosters that gets me there, i need to settle everything everywhere yesterday, and then pick 10 cities I need to grow.
As far as I can figure, a happiness booster city of size 1, with 2 hammers in its own tile and 2 hammers in the tile it works will take 180 turns to provide a net 5 happiness for no cost....
And then...that strategy would pretty much just be a slightly modified infinite city sprawl wouldn't it?
Gah.
Suggestions requested =P