Would Like Shipping Discount Addon

From time to time the companies I use send me vouchers for discounts on sending parcels. That's great if I happen to have an order I can use them on but I've thought of a better way to use these.

Shipping Discounts !

The theory is your visitor adds items to their basket and then checks the total price including delivery. The delivery is too much so they go away. But what if you had a short term discount for delivery. “10% off delivery to your country till 2nd Feb” or “Delivery of this item is discount today save £5”.

In the admin end would need a box in to put in the discount cash or percentage and tick list for shipping zone or countries it applies too.

Any thoughts ?

Why not use the built in promotions?

Do they allow me to pick shipping zones ? must confess I've not checked and won't be doing this till next year.

I will get discounts for international order but often not default country.