why are you so sure that the universe is expanding? the only evidence for a big bang is the doppler effect of the light from the surrounding stars and galaxies. What if this effect is caused, not by expansion, but by the pattern of light slowing down as it enters our galaxy.
It makes equal sense that if manipulation of space is possible, then space itself is a force occupied only within a galaxy. The goal would be to create a void within space equal to that outside the galaxy (where there would be no gravity.) This idea is based on a non-gravity universe, where gravity only exists within galaxies.
Therefore galaxies do not attract each other, and do not risk being hurled into a big bang. Instead they are freely floating in a nuetral environment where light can travel much faster between them.
Light then slows down as it enters the force of a galaxy and creates a pattern we see as the doppler effect.
This means that light speed is related only to the amount of galaxy force it is traveling through. If you create a void within the galaxy force, then light could travel faster, and then relative to that of course, would be time travel.