At the least light should escape a wormhole, and we should "see" what is on the other side. Otherwise I'm not sure how it'd be possible to detect any difference between a wormhole and a blackhole.
/s (Sort of.. not really)
You can't have that all in a single star system.
Frankly I find that whole set up only slightly more plausible than some kind of FTL, especially since they also have gravity manipulation tech already.
That said recent talks about habitable zone around a black hole made me wonder if that would work.
Good point.
Perhaps in the far future there will be a Find a wormhole challenge where future human teenagers will dive their spaceships into a blackhole they think is in fact the entrance to a wormhoe and scream YOLO just before entering the event horizon.