One thing that has always annoyed me is that you seemed to have to have a tow bar (dragkrok in Swedish) on your car to be able to fit a bike mount. And tow bars are not that common, there are several good reasons not to get one, like added cost, not usually available on used cars, and that they compromise crash safety to some extent. But to put my bike on a car it seemed that I had to get one. I was thinking about how to build a bike mount that could actually work on a regular station wagon by making use of the cargo rails, in some clever way.
But it seems I do not have to invent and build and market this thing myself: it is already available! I found a whole set of varieties from a company called Thule when I browsed a biking catalogue recently. Seems to fit quite a few varieties of cars including even the odd sedan! Good to know that they exist if I ever need to carry bikes regularly.