Please don't go overly complicated with game saving. Start small, release, expand/fix later. Don't try to save complex stuff from the start (let game lose some data); saving/loading just structures, resources and where/how many units there are - will be more than enough for now! Even just structures will be ok for first release.
I say that because serialization can easily become very complicated, especially when you want to save graphs (ai planning states) or object references (guaranteed duplicates when deserialized naively) - headache^2, don't even go there right now!
Oh I remember the pain I had with restoring references between saved objects in previous game I made (Pixel Pirates 3D) :D
Just like you said, I'm making it simple and may leave it that way with a bit of storytelling:
'You're not loading the game, but moving through time and space, generating energy blast wherever you happen to appear. Everyone there stops in confusion'
Going back to progress I made - I have already saving of station grid (build modules & trusses), mining settings and units. Before releasing first version I wish to add saving of devices (with their content), planned constructions, earned cash and current cycle.
Second release will have asteroids, contracts & visitors