Back in 15.03, it was possible to optimize motor ignition delay in multistage rockets. Shortly after that release, the FlightConfiguration code was rewritten, and at that time the ignition delay optimization was commented out with a "TODO: reimplement motor ignition optimization" comment inserted (see 1401d99#diff-74b90278caf9ed3d976b46e128c16e5ad585fdfda437d4fdfc546b940921dc28R192 ) but then apparently forgotten. We ought to reimplement that.