I think people do not comprehend just how ridiculously big a Dyson Sphere is.
The most generous estimate of the size of the Galactic Empire I could find indicates that it extends across maybe fifty million inhabited worlds -- 1 million "member" worlds, and the rest in "colonies, protectorates and governorships".
http://www.theforce.net/swtc/astro.html#galaxy
At a diameter of 2 AU, a Dyson Sphere has an interior surface area
550 million times that of Earth.
*550 million* times that of Earth.
Think about that.
You could probably take every single one of the Galactic Empire's fifty million inhabited worlds, apply its surface to the inside of the Dyson Sphere, and still have roughly 90% of the thing left over unused.
Let me put it another way:
It is very likely that the entire population of the Galactic Empire could live comfortably in roughly 10% of the interior surface area of a single Forerunner Dyson Sphere.
And that’s *one*. The Forerunners built *many*.
On top of that, the Forerunners had the technology to take a megastructure that colossally huge, and
move the entire thing into a pocket of hyperspace, which just happened to make it essentially
invulnerable to attack.
They had the technology to sustain this hyperspace pocket for at least
a hundred-thousand years, with no downtime, staffing, refueling, or external supply and assistance of any kind.
We have no real idea what the Forerunner primary habitats or their actual warships were capable of, but given the technology level demonstrated by their mere
bomb shelters, it is *impossible* to conclude that the overall power and engineering prowess of their civilization is anything other than mind-boggling, and almost certainly similar in magnitude to the capabilities of civilizations like the Culture.