Maybe that sort of thing could be included, with other time-management considerations, in a different mode.
Also, Facebook "social" games are largely the sorts of things we should be avoiding, given their ultimate goal. As such, it should not necessarily play out in real time, unless you really want it to, so that getting a car imported, cleaned up, stripped down, modified, tested and finally raced would take months of real time.
I'd rather you just allocate that time to certain tasks and then move time forward in the game once you've done so. A bit like some older rally games used to make you do between stages, but here not just for repairing cars "in the field", also for everything you do in GT.