My expansion would be
1 New victory method: Corporations - To summarise, a corporation victory requires you to dominate in extracting essential global resources and producing them into manufactured goods which you export across the world to other civilizations. To do this you need to settle, expand and conquer the world to gain access to resources that your corporations can then use to sell to neighbouring Civs.
If you succeed in dominating in this area you essentially make the entire world dependent on your manufacturing economy and as this continues corporations essentially become multinational organisations but the total effect is to spread your civilizations influence and control over the world. I.e. every economy in the world becomes dependent upon your corporate economy and the transfer of wealth back to your Civ makes you stronger at the expense of other Civilizations.
So it sortof combines elements of existing victory strategies. I.e. you have to conquer or use diplomacy where needed to secure resources such as oil, rare-earth metals etc as these are essential to make high-tech electronic goods.
You need to pursue science in order to use technology to build an advanced manufacturing economy that is the envy of the world
Like culture you're pushing influence onto the rest of the world but instead of cultural art, music and fashion rather it is motorcars, TVs, stereos, mobile phones, computers, software, aircraft etc....
Corporations will be heavily associated with late game buildings such as banks, stock exchanges, factories, medical labs etc in a similar way that religion works with early game buildings.
Victory is achieved once your Civ gains supremacy in monopolizing world Corporations and thus you essential make every Civ dependent on your economy so every other nation becomes in-a-sense one-with-you, much like the Cultural Victory. However an economic victory requires much more aggression in securing global resources and perhaps involves destroying or embargoing other potential competitors
Update Science Victory - Science victories are pretty boring right now so a new tech age will make this victory condition more interesting (see space age - below).
2 new ages:
Enlightenment (new units: ship of the line, red coats, foregin legions, emphasis on colonization & imperialism) - I wont write too much else there cause others have already covered it. Important for Corporate Victory as you can use colonial/imperial expansion to begin controlling world resources and East India Trade Company's etc to begin monopolizing control over trade routes/luxury resources...
Space age/nanotechnology age (One more age after the Information Era). Unlocks more technology required for a science victory. Brings in Fusion Power, rocket-sled space launching, Atom-smashing National Wonder - required to effectively research Space-age technology, 3D printing, advanced robotics, Satellite warfare (enabling you to destroy cities and armies from space or spy on enemy cities), antarctic research station, nanotechnology medicine, railguns, heliaircraft carriers (the Avengers), terraforming, lunar mining, deep sea mining (essential to gain special resources to build colonist ship to reach Alpha Centauri), build a colony on Mars (Your new Mars city is accessed by a new UI that will give you a view of the martian landscape including resources and your city) and research advanced physics allowing you to fold-space so you can create a wormhole to reach and then settle Alpha Centauri (Both required to win you a science victory)
-New units to fill in the 2 new ages, new buildings, specialists and wonders to fit in with Coporations and the new Science victory, i.e. Nuclear powered aircraft carriers, helicarriers, hovertanks, military satellites...
-Order & autocrat governments can discover how to launch biowarfare/bioterrorism attacks on other Civs using spies. To do this they will need a special Black Ops building unlocked by the NSA.
A new National Wonder, the CDC (Center for Disease Control) can be built after ecology (requires Medical Lab). This building enhances effects of Medical Labs and has 2 specialist slots for Medical Scientists, they cost gold to employ but yield science and also reduce the damage of a biowarfare attack & investigate the Civ that is responsible.
The NSA has more functions and also works to prevent bioterrorism attacks by enemy spies. It has 2 specialist slots that cost gold to employ but increase the effectiveness of your spies in other cities and also work to prevent home bioterrorism.
-many new resources (required for corporate victory); tea, coffee, cocoa, tobacco, opium, Rare-earth metals, mineral sands, platinum, thorium etc
-Enhanced Economy- Civilization Health and approval rating factored in, Now taxations is introduced, more dynamic economy and infrastructure management required (this is essential to progress into the latter scientific ages i.e. your science will start falling off if you neglect medical research centres, Civilization health drops, set taxes too high, high unhappiness and wars, or lack access to required resources etc.
The efficiency of cities will start to drop once they grow past a certain size (this means that tourism, science, health, happiness, productivity and corporate growth will start decreasing significantly). Fxing/treating this requires a significant investment in capital works projects such as a new City Motorway Network (Refrigeration), Suburban heavy Railway (Railroad - cheap in smaller cities, efficiency drops as cities grow & maintenance rises sharply with population growth), Underground Railway (Industrialization, Railroad & Factory - more expensive to build but cheaper to maintain & provides a stronger benefit for larger cities then the suburban railway) and Rapid Mass Transit (Ecology - more efficient & cheaper to maintain then the other 2 railways).
These systems are critically important if you wish to puruse an economic or science victory as corporation & tech growth depends on good infrastructure.
Also as cities grow, city connections will grow more inefficient so railway connections, Interstate Highway Network (Combustion) & High Speed Rail (Ecology) are needed to help here.
Other new buildings included is the Arcology, a huge superstructure; essentially a city within a city that increases a Cities population, reduces pollution and congestion, raises efficiency of specialists and corporations, this is essential for a winning late game victory.
Hydroponic farms a building that provides food for arid cities or your martian colony
-Old buildings like the granary, watermill & marketplace need to be replaced as you advance, probably into a Supermarket (at refrigeration) & the Shrine becomes a Monument to your Religion once archaeology is researched which yields an extra free culture point.
From these techs on you can no longer build these 4 buildings only the supermarket and build straight to temple.
- Health is a factor that affects the efficiency of your population. The earliest way to improve health is by aqueducts but later it is improved by certain technologies & buildings such as hospitals, universities & research labs...
Each city will research Medieval Age technologies 10% slower without Aqueducts, Atomic Age techs 20% slower without Hospitals, Information Age techs research 20% slower without Medical Labs & all cities research is decreased by a further 20% until the CDC is built. These penalties stand for all following tech ages if they are missing.
Researching Space age technology is reduced by 80% until the Atom Smasher National Wonder is Built. The Atom Smasher is a National Wonder with 1 specialist slot, is very expensive to run and must be worked to negate the research penalty to late era techs...
- Happiness should be reworked. It no longer decreases growth - seriously nearly all the countries in the middle-east have happiness issues (except Israel) and doesn't effect population growth in fact it seems to ,increase it. I would have unhappiness increase pop growth heavily but heavily reduce science, productivy, food yield and gold income instead as unhappiness increases. Left unchecked your population will grow but your food yields start to drop and your nation will starve & become a basketcase.
Social policy's to be rebalanced and some ideologies to carry a cost/benefit tradeoff. I.e. a policy such as universal healthcare would improve civ happiness and health (which helps science progression) but costs squillions to afford...
Move Rationalism to the Enlightenment age and Put a new policy tree Colonialism/Imperialism in the Renaissance age.
Rebalance Civs, tweak Vanilla Civs to make them more interesting and improve some of the weaker Civs like Denmark and Byzantium