I don't like the changes to missile engines. The old system, where you had a flat multiplier for engine power, seemed to make more sense, and it's less likely to create odd results. Missile engines will be designed differently from ship engines. This happens in real life. Only penalizing boosted engines makes multi-stage missiles more likely, particularly with the changes to launcher ROF (which I am very much in favor of, BTW). A flat x2 to fuel burn would make the whole system make more sense.