I hope this can be added. And it provides a use for Oxygen, since ore refining generates such a large amount of surplus Oxygen.
Also, it’s actually realistic for Oxygen to increase the energy yield per fuel. Because with air, a significant portion of thermal energy is wasted heating non-reactive parts of the air (mainly Nitrogen). A larger volume of exhaust gas is produced, at a lower flame temperature, taking away more energy.
Perhaps some kind of “Advanced Burning Box” can be implemented? Possibly requiring Oxygen and EU input, and supporting built-in igniting and extinguishing, controlled with redstone signal. Stuff like Coal Coke is actually viable as late-game energy source, only hindered by the difficulty controlling burning boxes.