@Morningsider
An excellent argument. It would be interesting to know how much those arriving by private automobile spend compared to those arriving by other means. The answer to that question might well make your case unanswerable.
Real world retail businesses in the internet age rely on the experience being pleasant enough to offset the additional cost and hassle of coming into the city. Being able to wander around pedestrianised streets and have a drink are surely key to this. It's why European city breaks are so nice. A car is a hindrance if you can get in easily and get your purchases home easily by other means.