product.product reuses most of the product.template views however some parts need to be excluded or replaced.
Instead of adding template only parts in base view and removing it for product, split the views in 'common' (product_template_form_view), 'template only' (product_template_only_form_view) and 'product only' (product_normal_form_view) where the first is inherited by the other two. The attribute mode='primary' on both second views allows to make sure that future inheritance of product_template_form_view and product_template_only_form_view will work with the full rendered product_template_form_view view.
This allows us to have valid buttons in crm for bill of material (filters based on active_id).
Also cleaning the mess with circular dependencies.