Hello all!
I ABSOLUTELY LOVE the premise of this game. It is very similar to a game I have been thinking about attempting to design myself! I am an astrophysicist turned financier, and I love everything you have contemplated thus far!
Questions: Have you considered having financial firms (Investment banks, or simulated individual investors, ect), in order to support a fully balanced, authentic free market environment?
Concern: Without a lot of liquidity in the modeled stock/commodities markets, you will be forced to create algorithms that approximate a free market environment, without actually having one.
I have already been messing around with Java, in order to code a fully simulated free market environment where individual people create a dynamic free market as the backbone of a similar game. Unfortunately I am not a professional programmer, so it would be much less work if this game were to fulfill my geeky aspirations! 
Idea 1: I suggest having several competing (NPC) investment banks who's sole purpose is to turn a profit. They are not interested in buying stock in a company who is clearly struggling, who probably is not issuing a dividend, and whose stock is over valued due to competitors buying up their stock. These banks will likely sell their stakes when stock prices are over valued, helping to keep the stock price from heating up too much during a feeding frenzy on a weaklings stock. On the flip side, they are also likely to buy up stock of under valued companies early game when everyone is more concerned with getting their internal systems running. This could even be a source of early game funding, as selling stock to an investment bank early would give you more capital but would be risky later game as you now no longer have control of that stock.
Idea 2: Simulate (a lot of) individual, high net worth investors, doing the same thing as Idea 1. Possibly, when a player is "bought out," they use these funds to become an investor? Maybe even buy themselves back into a controlling interest of a company as a way of re-entering the game?
Idea 3: I hope that you are considering incorporating a dividend payment system. This is a great way to support ones own stock price. Or at a minimum the ability to buy back ones own stock to keep the price high.
Idea 4: Allowing the issuing of Bonds, could make for some very interesting strategies. Desperate for capital, one might be willing to take out a loan that could be crippling down the road. This could fit in well with Idea 1, or you could even create a fully dynamic bond market. Though maybe that would be a better fit for an expansion.
Idea 5: Allow players to take the investment bank strategy themselves. In order to make money as this kind of corporate strategy, I could see the need for a expansive financial ecosystem, possibly larger then just 8 players worth of stock and commodities... purchasing stock that produces dividends could help significantly, and a fully functioning bond market wouldn't hurt as bonds also produce revenue for the owner.
I envision a playable strategy could be to sell a large amount of your stock right away (or possibly get a large loan), take that cash and start buying and selling other people's stocks, commodities or bonds. If bought and sold at the right time, you could turn a profit without ever having to build a single mine, employ very many people, or even have much property. You could run lean and mean, and attempt to topple your opponents purely through financial wizardry... If there are enough market makers to create an authentic balanced free market (possibly by simulating a population of high net worth investors, as in idea 2), then this would be a very enjoyable strategy for myself...
Just some thoughts. I love Stardock and I'm stoked to see that this game is being developed. PM me if you want to hear more of the ideas I've developed personally regarding this kind of game! I would be very willing to collaborate!
-TheTraviler
