The pizza company pays the delivery driver an hourly wage and possibly some compensation for mileage driven. The tip is added on top of the base compensation.

The pizza company pays the delivery driver an hourly wage and possibly some compensation for mileage driven. The tip is added on top of the base compensation. Your proposed simplest solution isn't guaranteeing a minimum tip. It's saying that the first $x of a customer's tip will go to the company instead of the employee. This is theft. The company already charged the customer a fee for this service and should be using this to pay their expenses.