I think that with the very constricted development resources available now for car-player releases, it wouldn't make much sense to implement something that can be perfectly emulated using existing features. Can't you just divide these FLACs up into individual tracks? Surely cue-sheet FLACs are just an ugly workaround for players which, unlike the car-player, are too feeble to play normal FLAC tracks completely gaplessly?

Peter