It is not possible to completely void space. In fact, if you and your friend each have a Geiger counter (a particle detector) and yours doesn't go off (so you see a vacuum) and your friend accelerates with their Geiger counter then their device will go off, i.e. they won't see a vacuum. And if you adjust your space so that your friend's device doesn't go off (so they think there is a vacuum) then your device will go off, so you won't think there is a vacuum. This is the Unruh effect, it has a similar basis as Hawking Radiation from black holes (accelerations are similar to gravity).
So two observers that are accelerating differently will disagree about whether there is a vacuum, they won't both see a vacuum.
And even if you could make a super vacuum, it would not make light go faster. It is in the nature of light to go at speed $c.$ The vacuum is just what allows things to move the way they naturally move, and light naturally moves at speed $c.$
But what if you tried to find something other than light that moved at a faster speed? It turns out that if you could alter the properties of space to allow something (even pure information) to travel faster than $c,$ that you could use this method to send information backwards in time.
Literally you could read the stock prices tomorrow and send the information back to today. I know it isn't super obvious, but we've done the physics to know that if we could do a faster than $c$ transmission we could send information back in time.
It is similar to those different observers disagreeing on whether there is a vacuum, except this time they just need relative velocity and don't need relative acceleration. You carve out space between here (and tomorrow) and some distant place and someone else carves out space between here (and today) and that same distant place. But if those people are moving relative to each other, their disagreements about motion means that when something faster than $c$ from their point of view, the thing is moving just right to go from here-tomorrow out to the distant place and then to turn around and come back to here-today. The whole idea that the universe all experiences time the same way died over a hundred years ago.
Again, you'd have to study relativity to see how to figure out which paths and how fast those people need to move and in which direction. But that's how bad it would be if something went faster than $c.$
So even making a theory where things move faster than $c$ is hard because your theory then allows time travel, which makes it hard to do experiments if future things can affect your experiments. So we don't even have a theory that allows such things, because we don't even know how to do that. We have actual experiments showing that time behaves differently for different observers, and the experiments are quite detailed and don't allow much room to wiggle.
So even if something experimentally looks like it might be going faster than $c$ we look for every possible other explanation first. And we've always found another explanation.
So you can't make a super vacuum. And a super vacuum wouldn't make light go faster. And trying to make anything go faster than $c$ would be as hard as making a time machine. Time itself behaves differently rather than allow things to go faster than $c$.
For instance you might think that shooting a laser on a high speed train might make the light go faster $c,$ but time itself will pass more slowly on the train to prevent it. I want you to know how big a claim/ask/discovery you are talking about.