Add or Remove Variants Automatically (via CSV) in already-uploaded Products

Hello everyone! The company I work for has a horse riding clothing website. Once a year the catalog changes: some colors are removed and others are added.

The products always remain the same, but the variations within them change.

Is there a way to do the change-collection automatically, without having to go manually to load the new variants and remove the old ones? A ready-made CSV file comes out of the ERP, but the integratedShopify procedure for uploading products does not remove or add the variants found in the file.

Has anyone ever had this problem? How do you usually manage the change of collection and variants for products?