you will need to redo the logic for your shipping rules to accomplish this.
also, you will need to add a new column to the cart object. for the sake of example, call the column "shippable" In the add to cart behavior for items that shipping applies to, set the value of the shippable column to 1. for items not included in the shipping, set the value to 0.
In the shipping rules, use the trigger:
"Number of items with a specific column value"