would that really be difficult? im thinking about something really simple and 2D like the porsche logo:

you would only need to create a series of flat fixtures with a few different shapes (round, oval, square and rectangle), the texture of which would be "emtpy".
the decal texture could then be specified when you begin a game and set up your car company, like in other games where you can use your own decals.
most tycoon style games really suffer from terrible generic logos supplied with the games.
i think that would be a small but nevertheless very effective feature to individualize our car companys,
especially since manufacturer logos are rather important for real car brands.
the logos could also be used to appear in other parts of the game (marketing, dealerships, outside your factory etc.)
even more awesome would be a kind of dynamic lettering fixture, where you can enter your car's name or specification and a fixture is created which you can put on the back of your cars.
but i fear that one would be really a bit more difficult to put into the game.
cheers,
stonelouse