Here's the problem. Converting energy into matter is very difficult, as it requires a lot of energy to create matter. According to E=mc2, one gram of matter requires energy equivalent to 89.9 terajoules, or 21.5 kilotons of TNT, to make. Reasonably, ether would take a lot more energy to create, especially if it can only be man-made.
Matter is a type of energy. The only difference between the two is that one has mass, and since it has mass, it has volume. Is ether a type of energy, as well? Today, we know that there are two types of existence: energy and matter. If we make a third kind of existence, then we might have to rewrite a lot of science as we know today, possibly all of it. How will ether change quantum mechanics and quantum physics? What are the equations of the equivalence of ether and energy, and ether and matter? How will this change force, as force is a product of mass and acceleration, and mass is matter, and acceleration is energy. How will this change momentum? Is ether unstable? If so, then what is the half-life of it? Would this support or contradict String Theory? I could go on, and ask so much questions.
Instead, let's do something more simple to do. Why not make ether a type of energy, like Ether energy? It won't be a new type of existence, but it would be under the category of energy, and makes things easier, and hey, I would approve it.
The link that K2 sent you, that supposedly said that it takes time to convert matter into energy, does not include anything about if it takes time to convert matter into energy or not.