Cart discount control

When using the cart plugin you have a option to "Discount ticket fields prices" YES/NO.
Thats great - BUT - we could really use a feature were one in the field itself could exclude it from the discount calculation.
The scenario is that we use one field for the tickets were we want to be able to apply discounts, and we have another field for add-ons like program and other merch that we dont want to apply discounts to.