So, I was watching King of Queens with my grandmother not too long ago. One of the episodes involved playing the stock market, and I thought "Why not have that in KSP?" I mean, there are different agencies, and then there's your own agency, most likely named "Default" for you sandboxers.
The idea I'm pitching here is a stock market in-game that mostly depends on the reputation system. If your rep is in the neg, then there is no chance for investment. The higher it is, the higher your chance. If you buy parts from another agency, they gain the profit for the sale, unless your agency builds it's own parts, either requiring EPL, or just a simple toggle option. Of course, this could lead to a career mode that is just too rich, especially if you're the Astrogamer, Scott Manley.
Perhaps there could be a button found in the Administration building to access the economy, or maybe even another building added in. Maybe RemoteTech's developers could have a helping hand in this, with certain areas of Kerbin needing connections because of where other agencies are located at. Maybe even some world record contracts for gaining however much money from the market would be a great addition to a great mod.