Mentioning system update

You should have a  way to configure roles so they can ping other roles but not everyone or some other role. I mean, you could select what roles can one role mention. For example: Role A would be able to mention Role B but not Role C and not everyone. 

But role C could be able to mention everyone and role B.

This would be really helpful to prevent a role from mentioning everyone but being able to mention a specific role.