Hi Sébastien.
I am sorry too.
I checked your patch files and it seems most of them are included into the code. But if something does not work as you expect, there is surely something wrong somewhere with this feature.
We make a very big clean of code and uniformize a lot of field name into 3.4, trying to not break even not common features. Our main problem is that the npr feature has so few users using it than we don't have test unit for it to check feature is working correctly beteen each versions, and don't get bug report to check it.
Is the problem on all npr vat management (supplier and customer invoices) or only supplier invoice ?
I think your patch is still here but a regression appears at one place. It is enough may be to break all feature, but i don't think all your patch is lost. Your help to localize regression is surely appreciate (we don't have people knowing this feature like you in our core team).
PS: Don't worry for french. As you said, this feature is used only by french speaking people. Also i prefer your help in french than no help at all ;-)