I would love to see this become a reality. Does anyone know how many people are part of this idea so far? I know the stats on the forum say that 200,000 + people have registered but not all of them can be current. I ask because the idea of seeking donations to start this up might be in order.
In the mean time, some one should start compiling a plan for the game. Get all the ideas of everyone together and break them out into sections; zoning, traffic, government, etc. Then post the plan and start getting feedback or even voting on how these things should be implemented.
Once the master plan is up, then we take the money and hire some programmers or contract with an existing game or software company and then work out what we can do and what we can't do. Once the limits have been addressed and everyone agrees, we code the project.
If this game goes to market then the investors get a return based on what paid in. Not sure how that would work but what if 10,000 people each put up $100, produced the game and were able to sell it? We become share holders in essence.
Don't feel overwhelmed by this. If Linux and open source can thrive on donations then this can too.