I especially like orost's idea of it burning CR especially -- it also ties into the concept that harassing the enemy as they try to flee causes them to lose additional CR for a slight loss in your own CR, as you're giving just enough of a pursuit to force them to throw extra books into the fire.
In the long run, being able to burn off CR to achieve higher speed is also just a form of burning additional cash, in the form of supplies, but since it has additional side effects beyond a mere financial hit it's both simple and elegant. I suppose it boils down to "is Infernium fuel specific to hyperspace ONLY"?
The only sticking point I can think of is trying to teach the AI when it's smartest to use the feature and when it's not smart to use the feature. There could also be several circumstances of ragequit-level annoyance where a massive fleet travelling at burn 2 suddenly jumps to and catches you at burn 4 just because you grazed a little too close in your burn 5~6 ship. It would have a strategic element to it, of course, but part of the reasoning behind the removal of the post-combat deceleration (which I'm still not fairly happy about unless/until we get nearby ships able to reinforce...) was that it wasn't explained anywhere and could be frustrating at the entry level.
