It would be nice to have the possibility to use BeamNG Drive to author and develop custom racing games with limited selection os cars, tracks and modes (circuits, tournaments, a career, etc.). I only can imagine the oportunity to reproduce classic games like Need for Speed II, III, Test Drive III and so many other classics in a so good engine! It would be a new category of mods and maybe it would rise even more the community.
Nothing is stopping you, as long as its just a mod pack and you're not planning on selling it as a commercial product.