Do you remember when restaurants smelled good? The place was filled with the warm smell of delicious food. Maybe butter or beef or even french fries. Those smells are mostly gone now. The need for huge fans over stoves to suppress fires means that if the food smells good the odor has gone through a filter to satisfy the EPA and then up a chimney somewhere. This problem is an opportunity for an enterprising entrepreneur. Why not build a device that generates the smell you want people to associate with your restaurant and injects it into the entrance area.
This Bradley Smoker was in front of a BBQ restaurant and really made me salivate. The “Aroma Generator” TM would have to be fire safe and EPA approved. Perhaps it would need monthly service with the appropriate “Aroma Cylinders”