This is why I believe we should focus on the concept of superior organization instead of the specific time period or units.
That's fine, but we don't have game mechanics that represent organization well, and I haven't seen any suggested mechanics that would model this well in a way that would be good for gameplay.
I want to find a military in history which used better organization to combine fast mobile and ranged units (like Germany).
I think it is a mistake to think that German strategy, or superior organization in general for any civilization, necessarily has anything to do with "ranged units". Remember that ranged units in Civ5 are really indirect fire weapons - artillery, and archers - and that what counts as a ranged unit is on a sliding scale that varies over eras. Rifles and tanks aren't ranged, even if their weapons shoot further IRL than an archer does.
What civilization would make sense for combining mobile with ranged?
Why is this an appropriate goal? What does this have to do with organization or effective officer corps or good communications?
The strengths of the German WW2, and in some periods the US military, were based in part on well trained officers that had a significant degree of tactical autonomy. Get good people, put them in the field, let them make decisions.
This doesn't have anything to do with good use of archers or artillery.
And why would this be fun? Ranged units are already very powerful.
Really, superior organization probably just results in higher strength, or possibly higher bonuses from flanking (superior communication and coordination makes a flank attack more effective because it arrives at the right time).
I gave the Ottomans a Liburna because it's fun to use with their ship-capture ability. The other Ottoman bonuses are valued low by most players, so I figure things balance out in the end.
I'm ok to leave it for now, but the problem is that it gives tremendous early game anti-coastal-city power.
The GP-based ability I'm thinking of is something like +X% GP rate per major civ alliance, and we get free great people from citystates (similar to the Immigration policy).
I think mimicking a social policy isn't very interesting, but overall something like this is fine, with the caveats above that diplomatic bonuses make sense for very few major civs.
I feel the key problem with melee ships is they are good at capturing cities.
That's part of it, but the move after attack that allows for hit and run is also a big problem, because the AI naval performance is so limited by its sight range. If it has ships nearby and sees your units, then it will attack, but if your units are outside of its sight range, then their ships will just sit around.
I'm fine to leave Iroquois for now; I don't have recent experience with them, I need to test them before forming an opinion.
I like Washington because he's the best leader for early fast expansion. His ability lets us find city locations and grab the resources we want faster and cheaper than any other leader.
I just really don't find that at all. Early expansion isn't limited by sight range and movement speed, it is limited by happiness. So I don't find Washington's abilities to be helpful at all, and I think they have terrible flavor in representing why the USA matters in world history.
However, the US had the characteristics I described long before the US became the dominant world power in the 1940's. It was a destination for immigrants for centuries, and scientific innovations like the telephone and Henry Ford style assembly line production occurred around 1900.
The US was a minor power until the late 19th century, when the truly massive immigration flows began, and when the economic and industrial strength began. I agree that these characteristics predate the 1940s, but they don't predate 1900 by much.
Ragtime was not an important part of American power or influence; American music wasn't a really big deal internationally until post WW2.
Ethiopia's tall empire theme seems like a good fit for the great person alliance bonus, since GPs are ideally suited for tall empires.
But there is no historic flavor for Ethiopia being an alliance-broker.
Instant gold would be interesting on the Paper Maker. I'd been thinking about giving an effect like that to someone.
That doesn't seem very flavorful to me. And China if anything should be about patient, slow, gradual accumulation of power, not instant boosts.
What sort of scaling issues do you have in mind?
A free luxury resource from a UB becomes a problem when you have lots of cities, because you get too many copies. A unique improvement would be even worse - particularly with the Commerce policy that gives happiness even for excess copies of luxuries. I could spam the improvement everywhere and have infinite happiness. Tying it to a building also prevents a Tall playstyle - and certainly the Netherlands of all civs should be able to build up a big economy without needing a lot of land.
I like the idea of having it as part of the Dutch UA, where you get an extra copy for each era.
An infrastructure bonus sounds interesting for the Dutch UA. The combination of that and the Polder gives them the theme of "better infrastructure."
The Polder is sufficient to model Dutch infrastructure IMO. I would prefer that the UA remain trade/luxury related.
Yes, let's try to buff embarked defense first
Agreed.
China could be feared with such a bonus, and the Art of War does somehow advocate Mobility, no?
The Art of War already seems to model superior organization and leadership to me.
I'm really lost as to why we need a civ that focuses on foot archers and cavalry. Those just don't really go well together.
As for an economic bonus, the problem I see is rather to find one that is distinct and is strong in the late game.
Gold per pop on a stock exchange UB.
"improved ressources with acess to fresh water give +1 "?
Probably too strong, especially in the early game, and favors rivers and lakes rather than coasts, which goes against real world Dutch flavor.
Free aqueducts doesn't make sense to me; if any civ gets an aqueduct bonus it should be Rome. I'd be tempted to drop the ballista from Rome (it has poor synergy with the Legion anyway, and isn't nearly so iconic) and give them Cloaca as an aqueduct UB that gave happiness per city, to help them build a sprawling empire.
Mitsho, I don't know how a combined engineer/scientist would work
I think the idea is to simply give Germany +production on engineers and +science on scientists, or vice versa. Similar to Korea.
In fact we could just limit it to engineers to make them more different; bonuses on engineers and manufactory great improvements.
German engineering is very much an iconic thing.
still think they need the other 2 promotions to make it practical as well. Specially since the naval buff.
mounted reduces demand for ranged units, while Persia's +1
and +1
farms, a unique National College giving +2
every time a GP is popped? Would work with the Nobel Prize theme (prestige from giving the prize to foreign great people). Though that obviously works also for Ethiopia, maybe with 
instead of :C5culture: and the idea that it gets you closer to the next Great Person... Though maybe 
