To create ‘protocols’ often causes more problems then it solves. To line up the employees and say, “Do not stop working to make your lunch order. Do not ignore the customer to make your lunch order,” will not have the required effect.
By having lunch orders made as the person checks in will solve the problem. No discussion, no reason, just change the method.
With customers bringing their own bags, have the standard be the packer asks for the bag before the cashier begins to work.
In this way, there is no change from the previous method of the bagger putting the goods into a plastic bag now into a cloth bag.
Further, by the bagger focusing on the goods the ability of the dishonest customer to practice a sleight of hand is removed.
As an addendum, never have a cashier begin to tally goods until the previous customer has moved away from the counter.
Many customers will steal the next customer’s goods if given a chance.