request: Free Shipping, but by country/zone

(Version 1.56 because I dread having to alter everything yet again with a new 1.57 install only for 1.58 or 1.6 to come out)

Could there be a way to specify Free Shipping levels by country? So that I could offer a region-specific Discount Code to e.g. local UK customers Free Shipping at £25, EU countries shipping at £35, USA shipping at £50 etc. In the form of discount codes that specify country of shipping as an option like they do minimum order, I was thinking, one could list country codes to be applied as per shipping modules when creating the Discount Code, much like you can set minimum purchase, uses per customer, etc. Possibly by setting up zone lists (I have all the EU countries under an 'EU' Zone in the admin)

For instance, in the Royal Mail Big Shipping module, it is split into the various world zones that UK royal mail use (USA gets its own zone these days, and costs a small fortune to ship anything to since they walked away from the previous global shipping deal they had) - each of those zones varies MASSIVELY in price, so this means a nice code offering Free Shipping to all orders over £25 might only cost me £4 in UK shipping, but it could be £11 to ship that same order to the USA, which obviously is not cost effective, so the one-size-fits-all Free Shipping option on the existing cart doesn't work so well for worldwide orders.

I couldn't find anything in the available add-ons by searching, but the thought occurred to me and I thought I might as well throw it out there for you incredibly clever coders who like a challenge, in case it was a practical idea after all. Or if there was a way to do it already that i simply wasn't aware of...

Any info appreciated!
thanks
Andy

Oh, wait, I literally just noticed that there's a Coupon Zone Restriction option, what an idiot. I guess I have to make a load of new Zones for the various countries in each now. Apologies!

(PS why are there are so many USA sub-zones included? As an international mail order business I just need the coupons to cover 'the USA' as a destination in general, not specific towns.)

Heresy Miniatures:

Oh, wait, I literally just noticed that there's a Coupon Zone Restriction option, what an idiot. I guess I have to make a load of new Zones for the various countries in each now. Apologies!

(PS why are there are so many USA sub-zones included? As an international mail order business I just need the coupons to cover 'the USA' as a destination in general, not specific towns.)
If you want to include all zones in the USA, just leave the zone selection as the (not well named!) Please Select. That will create enable a coupon to apply to any state in the USA.

Also possibly useful is Zones Shipping:

https://docs.zen-cart.com/user/shipping/zones/