Change the user group after using a specific Coupon

-- HikaShop version -- : 2.6.4
-- Joomla version -- : 3.6.4
-- PHP version -- : 5.6.27
-- Browser(s) name and version -- : Firefox 49.0.2
-- Error-message(debug-mod must be tuned on) -- : No errors

Hello,

I need to change the user group of the users when they use a specific Coupon in HikaShop.

What i need to achieve is the following scenario:
- Provide people a 10% discount + Free shipping

Since it's not possible to have a "free shipping" coupon, i thought that i can change the user group of the users when they use a coupon code.
A free shipping method would be reserved to this user group.

Is that possible?
Are there alternative ways to solve this issue?

Thanks Nicolas,
in simple words, should this plugin change the shipping method according to the coupon code?

Is there any documentation about the coupon API?

Achieved it in a different way.
Used a Joomla! plugin to automatically assign a user group to people who register using a specific domain email address.
In this way i restriced a flat 10% discount (not a coupon) to this user group and then i created a specific free shipping method restricted to this user group.

@nicolas, it would be useful if in HikaShop ACL management there would be also the possibility to restrict a shipping method (or whatever) to "All levels except the selected" like you can do in the "module assignment" in Joomla!
Thanks!