The concept of Account to contain all different types of accounts becomes very messy trying to implement most times. Consider creating an entity named Vendor. This will allow the Account entity to be treated as customer as it should. Additionally, have the Vendor entity included in the customer data type so that it can be used as a polymorphic lookup included with account and contact. Give the ability to create marketing campaigns and emails since current only account, contact and leads can be used.

Producing a vendor entity aligns with other accounting systems architecture. It allows for better security control in the business rules needed to create a customer and a vendor which do not always align.