Andy, here are my corporations that I have in mind:
Drink Corporations: They can be Fruit Juice (Already in), Sports Drink, Coffee (Already in), Soda (Unsure), Mineral Water, and just plain ol' water. I know we have water treatment plants, but they need water to start out with.
Trains: Haven't trains already been recommended by Manny a long while ago, its a great idea, and I guess you can vary them.
Also, should hospitals increase the number of children born, and lessen those who die? I think it should have one more thing; increase the range of ages that sim citizens should give birth? They are having a long life? Also, this should increase retirement age.
Fertilizer: This is used in Agricultural Corporations to increase output.
Finally, we should have Federation/Common Market Banks: The CM may set a tax amount on how much money a member makes, like 1%. For example, if someone makes 10B profit, and the Fed/CM tax is 10%, then 1B would go to the Fed/CM bank, also, there should be like some kind of security to see who gets the money.
Please reply about my suggestions! Also, the customer service here is excellent! You are active, if not very active, in the Simcountry Community.