While I do recognize they are spacestations, they still used the same technology and hardware and rockets, and took place in the same timeframe-and where extremely simple and primitive stations launched in one launch, much unlike the multi-module stations of today, taking place in the same timeframe.
Now, how could this be implemented? Let's started with the obivous. First of all, there ill be a new catergory in "Earth Exploration Screen", titled Spacestations along with a short, quick description (Fig 1). Upon clicking "Space Station", you will be greeted by the standard GUI but modifed. (Fig 2). From there, you have the option to performing resupply missions to your spacestation (Which I have used Skylab for), for to launch a new one.
Should you attempt to resupply a station that is not present, you'll be met with a window that says "Unable to supply nonexistant station, do you wish to launch it?", followed by a redirection to the station launch R&D window.

Fig. 1, Hypothetical new menu screen for Spacestation Missions

Fig. 2, Hypothetical New Selection Screen for Missions
Now, what hardware should the stations utilize?
Skylab Launch - Saturn V, along with "Skylab" Module (Two Parts)
Skylab Resupply - Saturn IB, along with Apollo CM (Two Parts)
Saylut Launch - Proton, along with "Module" (Two Parts)
Saylut Resuppy - Soyuz
And also, a last question, will the "Apollo Applications Program" be inside Episode One? I know it called for manned Mars and Venus missions, more Skylabs and a lunar base, but will be be a DLC, perhaps?