also, you should make it such as to create your next vessel (going from DGIV to XR2 for example) will require quite a few trips to a number of bodies. i should also add that its technically possible to get a DGIV or XR5 just about anywhere in the solar system if you use tugs and launchers, so encouraging this increases the variety of the gameplay of the addon.
personally, using the energia for an XR2, and the DG launchers doe the DG (duh...) might have to think a bit about the XR5 (maybe using the RATO and additional fuel tanks?)
and i think we should use raw resource types: Metals, Crystals, Rocks [if currency comes into play], plastics, liquids and gasses, then divide them into more individual resources, such as titanium, oxygen etc
also, i have had a thought: how about adding a "save game" functionality, it remembers the location of your vessel(s) (the one(s) that the module uses as handles) and puts them into any scenario, so if you dont want to use SCNeditor to save your progress, you could use a function built into the module
to explain:
after activating the module, you open a fresh scenario, containing only vessels such as space stations, then you begin a fresh "game" by choosing a starting craft, where the module spawns one at your chosen base (possibly adding a line to the vessels section of the running scenario to identify it as a [Addon name] craft
then, using the save feature of the module, it records the position of every craft that it is using. (it would be limited by logic to only those that are landed, so it couldnt be used partway through a flight)
what do you think?