If an item isn't being shipped using a physical carrier with a cost associated with it, would that not be classified as a transfer?
For example transfer Item X "Out" (from inventory) to location Y "IN" (home or a boat) + delivery (cost of delivery) = Z
Just create a new line item called "delivery" with an associated cost. Any item not being physically shipped can be transferred to + delivery= no more shipping confusion. If you add more than one shipping carrier, I believe like a printer you will always need to choose one, there is no method to default. If the cost of delivery however is a line item and not a shipper? That may be a work around to keep the associated delivery cost separate from an actual shipping cost, so things balance for you. (you may also be able to configure a custom button at that one store). Any transaction plus that button=delivery not shipping. Just a thought.