Adding non-territorial expansion to a game

I was thinking about 4X strategy games lately where one of the X consist being the word "Expand". On first, thougt, people always think about military territorial expansion, but there can be other type of expansion. For example, today, military expansion is not seen with a very good eye so there is little change in the political borders. But a country could still have a strong economic expansion without increasing the size of his country. This is for example the case of the united states which has a strong economic and political influence on the world even if their territory does not cover the majority of the world.

So I thought that the idea of expansion could be promoted in different ways than colonisation and military campaign. I was thinking at the different other fields where expansion could be possible. I found so far: Economy, Politics and Espionage. If you have other field ideas, let me know.

Now how could a system like that be implemented. For a concept like Economy, I did not want to keep track of all economic transactions. I wanted something of higher level and maybe more abstract that reflected the concept of economy. I thought of 2 properties:

- First the concepts increases in size when all civilizations gets bigger. But a civ's size is not proportional with it's influence.
- Second, A civilization's influence expansion would mean making other civilization lose influence. So you must expand at the cost of others.

Which means that the influence grow and civilizations try to fight for getting their share.

So the mechanic I designed could look like something similar to this.

The maximum economic power that can be allowed into play is equal to the total number of cities into play. So if you have 5 players which each have 4 cities, it makes a total economic power of 20. Now these points will be distributed differently among players. So the power distribution between players could be 7-5-3-3-2. So even if all players has the same territorial strength (4), they each have different economic power.

Now there could be various mechanics that could make these numbers grow ro reduce. First, if people colonize, the total amount increase, to that will leave unused power that can be acquired. Or players can fight against other players to steal their power. But at some point, when the whole world will be colonized, the toal power will always stay the same, so you will have no choice to steal.

Now what could be the effect of these levels. The usage depends on the game. For example, economic level could determine you money income or the number of building/upgrade you can maintain. Espionage level could determine the number of espionage cards you can play. Etc.

Finally, it would be possible to make treaties between players that influence these things. For example, I had a hard time determining how a trading treaty could influence the game (Gain additional money, have access to more resources, etc). Now it could simply increase your level of economy, or make some of your economic points impossible to lose. What ever the effect, this new dimension of expanding your influence increase a possibility of negotiation that was not there before.

So what do you think?