My go on this would be to limit it, because at some point I could't even cross the restaurant to serve my customers because of the gigantic queue xD
100% - there is actually already a limit of 6 customers in the queue and 5 customers in seats - if there's no places available in the queue when a customer arrives (or no seats when an order is taken) they'll just leave. But I only tested that behaviour in scene view and never actually checked if the player could pass the customers in line LMAO
Definitely would want to make it so the player and customers can pass each other if I go further with the project - though I also love the idea of having to throw the meal over the customers in the queue in order to serve someone in a busy restaurant!