Managing users with hostgroup inheritance

I currently manage users based with puppet based on node interitance.

All servers:
Base Users
DB servers inherit All servers:

  • DB Admins
    Web Servers inherit All servers:
  • Web Admins
    QA Servers inherits Web Server:
  • QA Users

Can I achieve the same thing with hostgroups and smart class parameters,
(Base, Base/DB, Base/Web)? I have tried overriding the smart class
parameter in Base/DB hostgroup, but I lost the Base Users unless I include
them in the override. I have many users and am trying to avoid having to
put all users in every smart class override.

I am testing using puppet forcge torancew/account module.