User registration only on selected category

Hi with Hikashop business I am looking for possibilities to have the user registration only on selected products or category. I have some products that should be able to be bought by guests without all the fuss of address and some products that need an email such as Akeeba subscription level.
I figure this can be solved with custom fields, but how can i make a custom field for an email registration that registers the client to my site and thus a specific subscription level or user group?
thank you, great product.

Hi,

This kind of feature will require custom code, a custom plugin should be enough to manage this.
Depending on the products present in the cart, require a registration or not by changing the option in the configuration dynamically.

It require good PHP knowledges.