@Kira and Nightfall: I'd be happy to referee a race or two, as long as you let me take a few laps too...
@Igiss: I have seen other mods where different engines had different cruise warm-up times. It's been a little while, so I don't remember which ones had them. I agree that the sounds would have to be changed for them, as some of the engines were set up to start before the sound finished and others after. The latter was particularly annoying, as there was a brief time when your engine would be silent.
All in all, if the times and speeds were changed, it would totally mess up some of the single player campaign. (Imagine getting to cruise speed a few seconds ahead of Hovis in mission 6, or worse, a few seconds after...)