Well if an alien race could plumb the depths of Zero point energy and tap the fabric of space time for energy then Dyson spheres become way too impractical.
Why not make a whole bunch of planet sized ships the size of mars or even earth powered by ZPM, have them be able to generate enough energy to create matter as energy and matter are interchangeable, E=mc^2. If I were them I would take my fleet of planet sized ships out to intergalactic space, ie. the big voids out there between galaxies. Then I would make more ships and make Hydrogen. eventually these "cosmic Hydrogen factories" could generate enough gas to give rise to new galaxies and stars.
What if the universe is like this. You have a metric crap-ton of invisible planet sized ships moving apart from each other and expanding space time while expelling hydrogen at the same time. And the expansion of the universe is due to these "star factory ships" moving apart from one another and not due to a "Big Bang". When they make a could of Hydrogen big enough for a galaxy to form they move into the next void created by their expansion and begin again. It would be freeky as hell if the universe turned out to be like that!
What other feats could a advanced alien civ perform?
They could jump into a basement universe with physicals laws that are same but with gravity that is significantly weaker or even non-existent. Because in a universe like that you could create objects the size of galaxies and you would never never have to worry about them gravitationally collapsing on themselves. Imagine a computer the size of a galaxy, in a universe where Gravity = 0 or 1x10^-10000000000000G, and the speed of light is 3.8x10^100000000000m/s. What could you simulate in that universe? Well, practically ANYTHING!!!! Add a few more spatial dimensions and you have enough space and power to simulate the entire lifetime of out universe from big bang to photon death in a few of our pico-seconds!!!!!
Could make for a cool Sci-Fi story.