I would like to have one content type "Basic" and then another content type "Premium" that has a few extra fields than the basic one. The idea is that I want my users to pay for premium publications (using Commerce Node Checkout Module) if they want to use those extra fields. Basic content will always be free.
It is very likely that I will need to make changes to the basic content type fields that I want to also be reflected in the permium content type. Is there a way to kind of "subtheme" the content type so that it reflects the basic one whenever changes are made but still carries a few extra fields that are independend of these changes?