@ Alpaca
I'm not convinced, but you might be right. It just doesn't feel right to me. You'll be able to squeeze maybe twice as much cities with ICS as I do with regular city sites (I tend to do them with 4 hexes between), but you'll end up probably with just around 50% more due to terrain features (mountains, barren peninsulas etc.) 10 highly productive cities are worth more than 15 weak ones in my book.
Within radius two you get 19 tiles per city, with radius one you get 7. So you get almost three times as many cities, not twice. In a more realistic scenario with coasts, city states and other surfaces you probably get maybe 9 tiles per city.
There are a few important observations: Firstly, city growth food requirements scale very strongly with population, I think almost in a square fashion. This means for cities to grow above size 10 or so takes a long time so you won't use half of these tiles anyways.
Secondly, the maritime city state bonus is per city. This means that two small cities grow a lot faster than a single larger one. The number of citizens that can work tiles will be much larger and the amount of science you generate will probably be larger, especially if you add libraries and set two scientists per city.
Thirdly, the bonus from the city tile itself isn't too shabby. You get +2f +2h +1g which is roughly equivalent to an additional citizen that generates no extra science. Once you build the forbidden palace, assuming meritocracy, this is essentially a free yield.
I just finished a similar game with France
Liberty - Piety - Order.
Welcome to the forums.
I'm unsure about the best choice, too. For me it's clear that you want to pick up liberty, at least for the settler production bonus. The 20% discount on buying stuff is very powerful because you'll buy a lot of stuff. Basically, it means you get a boost of +20% on whatever surplus gold you get.
Less road maintenance isn't that useful but nice, you save 0.2 per tile but we'll only have a bit less than two road tiles per city on average so you save maybe 0.4 gold per city per turn (let's say 10-20 gold). It's a bit more interesting for railroads. Last but not least, mercantilism will give you something like 10 happiness.
On the other hand, Theocracy will give you quite a lot of happiness, at least 30. So I could see skipping Meritocracy in favor of Theocracy. The problem is Theocracy has two pretty lame prerequisites and the rest of the policies in piety are very much not worth it. The +2 free SP is only useful if you go for a cultural victory because it will give you itself and its prerequisite for free.
In the modern era you'll probably not be able to afford to go both Autocracy and Order. I can see the sense in both but I haven't tried this often enough to testify which I find more useful.
Autocracy means you have to go for Theocracy at the start and lose the +50% settler production bonus (not very tragic at that point). What you get is a 33% discount on unit maintenance and bringing down your unit purchasing cost from 80% to 47% (or from 60% to 27% with Big Ben). You also get a nice -50% for occupied city unhappiness but I'd rather raze most cities and build my own instead.
Order, on the other hand, gives you +5 production per city, which is awesome, and another -50% to number of cities unhappiness. This is very powerful and iirc it's applied to occupied city unhappiness, too. You also get a 25% production bonus for every building you hard-build which is also good because we'll still be doing that quite a lot.
Overall, I lean towards order but could see being disproved.
Maritime food bonus is really what makes ICS work as you're getting +2/+4 food to every city tile way too early in the game (Communism is late enough that it shouldn't really be a balance problem) allowing the small cities to get to size 4 very quickly and build infrastructure fast because they don't need farms.
I agree that the way maritime city states work makes ICS a lot better. However, I think it would be feasible without abusing this because you would enter a regime where the free city tile production begins to matter a lot.