I've got a lot more to write about this, but here's my First List for the next Expansion:
Commercial Victory:
Which includes not just Amassing Gold, but also dominating the world's Trade System and establishing Cultural-Like Influence in all the other Civs (and a majority of City States)
"We're not only wearing your blue jeans, we're paying top price to buy them from you!"
Among the additions: Envoy-like 'units' like Factors/Agents who can establish commercial outposts in other Civs and/or City States from early in the game. Among other things, establishing Trading Posts to extend your Trade Routes: if there can be a Silk Road extending across Asia in the Classical Era, it should also be possible in the game.
Later, these Outposts could become elements in International Business (Corporations) which could be established by certain Great Merchants (Fugger, Rothschild, Mitsui, Vanderbilt, Rhodes, Harriman, Ford, Rockefeller, etc., etc.) These businesses would definitely include International Banking, one of the earliest major trans-national types of business, so that Civs and City States could borrow Gold - and other Cvs with the HQ of the International Bank could rake in the interest and other considerations.
Speaking of which, a revision of Resources, their definitions and placement, so that a Civ could establish early Monopolies for major Gold and Influence bonuses. Silk, Porcelain, Cheap Cloth, certain Dyes were all very lucrative monopolies for civs like China, Britain and Phoenicia at various times, and the possibility adds depth to the Trade system and new Focuses for International Business
And 'natural' Resources should be increasingly replaced and supplemented in the game by Manufactured Resources - Amenity, Gold, Trade enhancing materials available from Buildings and Technologies later in the game. Why shouldn't some Civ be reaping huge benefits from Automobiles in the Modern Era or Solid-State Electronics sold to other Civs in the Atomic-Information Eras?
(Historical Trivia Input: The largest car and truck manufacturers in Nazi Germany in the late 1930s were partly owned by - Ford and General Motors. And the largest tank factory in the Soviet Union: Zavod 183, the Kharkov Tractor Works, was an exact copy of Ford's River Rouge Plant in Detroit, built for the Soviets by Ford engineers - International Business and Profit make for strange Bedfellows, indeed!)
Part of this also is the enhancing of the Ocean: Sea Trade Routes carry more, farther, make more Gold than land routes until the Industrial Era (railroads). AND Settlers, Builders, and Recon units at least, can move through Coastal Waters from the beginning of the game - IF your starting city is in the Right Place (coastal, naturally). And similar enhancements/bonuses apply to Trade Routes traced along rivers, which should extend the routes and their returns greatly - again, until Industrial and Modern Era land transportation catches up with barges and boats in the ability to transport Large Quantities of materials.
Diplomatic Victory:
This relates to more than just Start the UN/World Congress, get votes. Internationally recognized 'norms' and laws started much earlier: like in the Medieval Era with Erasmus. It should interact with Warmonger Penalties, International Opinion of Civs based on their 'conformity' to The Rules - which should change during the game.
Just for an example, Borders will stop at the coast when the game starts - there was no Law of the Sea, nobody cared much who sailed/rowed by as long as they didn't stop and steal anything. That ties in with Making the Ocean Important, because you can explore almost anywhere by sea early on - until you run into Hostile Civs. City States, or 'Barbarians' - and ganging up against, or supporting, 'Barbarian' Pirates is another type of Very Early Diplomatic agreement.
The types of agreements throughout the game, then, should be more varied and potentially involve more than just 2 'players' - City States and 'third party' Civs can get involved - and you should be able to make Diplomatic Agreements with 'Barbarians' as well - for trade, alliance, or maybe just to sic 'em on your neighbor!
Mercenaries will not be just a word on the Civics Tree: you should be able to 'rent' your Units out, rent or buy units from the Barbarians, City States, or other Civs (wth varying degrees of restrictions, of course).
Some City States, in fact, will make a very good thing out of permanently renting out their troops - like Berne/Geneva with Swiss Pikemen, Darmstadt with Hessian Fusiliers, or Rhodes with Slingers. And the only way anybody other than Mongolia and Scythia are going to get Horse Archers is to ally with them, rent from them, or hire from the Barbarians! (Of course, if Shaka manages to hire some Keshiks, The Game Is Over!)
Once a World Congress of sorts is established, a lot of this will go through it: so getting condemned by it will seriously hurt you ability to make Good Deals (bye, bye Commercial Victory!) and increases your chances of being Militarily/Diplomatically Isolated (Hello 'Peacekeeper Forces' composed of Zulu Keshiks!)
Systems don't lead to Victories in Isolation: you will have to engage Diplomatically and Commercially to stay viable as the game progresses - and Religious Influence will certainly count Diplomatically as well!
More to come...