I'll add my 2 cents. When mining resources thus producing fuel becomes possible, it would be very convenient to have some way to transfer fuel and other resources from mines to space stations. To make it somewhat authentic, there could be a 2 part resource transfer module - one part (in shape of some rocket launching station) would have to be placed on the ground, and the other part (some special docking station) would have to be placed on space station. The process of launching cargo-rockets and docking to the station would be autonomous, it would not have to be visible. Another idea to increase the importance of space stations: currently there's too little profit from bringing manned or unmanned ships back to Kerbin. You can just land and transmit data over and over again until you drain all research points. If bringing your ship back would become very important, having a refueling station on low orbit would become beneficial as it makes such missions much easier. Also, in addition to research points, some unlocks should require completing some specific missions, which would involve some space station related activities.