A last question before returning back :
With my method, which is wrong bug, I can assign a brand, a color, a year to my products. I can see them on archive pages. I can see them in admin array (I’ve added column for attributes), I can even see them on custom template archives pages like taxonomy-pa_brand.php.
So if I override additional-information.php to get my fields instead of attributes list, I got everything I need ?