[khorboth]

I think you're definitely going about your world-building the right way. Start with themes and work backward to your world.

Here's my thought: How about if wormholes are present as a matter of stellar mechanics, but must be activated by a ship's drive. This is how it worked in A Mote in God's Eye. They link solar systems, most having one or two some having more. Sometimes, rarely, the opening is actually within the star's corona. There's no way to know from the far end, but it's a nasty shock when you pop out. Only very specially designed ships can even think about making such jumps. The Sol system is one such system. But only for another 25 years as the jump point drifts out of the sun due to the slow motion of the stars around us.

About 20 years ago, the smoking husk of a ship emerged from the sun. No survivors. But we learned a lot. We were able to reverse engineer the drive and several other systems. We learned about jump points and that aliens existed. We also learned that there was a ticking clock until massive alien contact was upon us.

Now, the most advanced human spacecraft ever designed dives into the sun to learn more about the greater galaxy. They have two primary goals: Acquire alien technology to advance the human race. Assess possible threats from outside our solar system. They are also under orders to protect the secret of our existence for as long as possible.

The ship is highly automated. There are only [players] crew members aboard. They're highly competent, but must fill all roles between them. They're the landing party, the bridge crew, the doctor, everything. Supplies are limited, and O2 is heavy, so fewer people means longer mission.

Once out in the galaxy, they find trading hubs, jobs to do in exchange for galactic currency, uneasy alliances, and also that many of the nearby systems are just unexplored. So, it would be a good idea to explore them.

They find their ship to be uniquely suited to some of these jobs due to the extremely heavy armor. Also, everyone assumes they are either a tough exploration ship or a warship from some unknown species due to the strangely tough design.

Now, the crew is buying/trading in alien technology, adding new weapons to the ship, navigating alliances with aliens of various psychology and trying to stay alive through it all. In between everything, they've got big question mark systems 2-3 jumps from Earth which could be uninhabited or could be secret pirate/military bases or could be the spawning ground for the dreaded crystal plague.

Yes, a lot of this is silly. But I think it gets you where you want to go.