Create a new rule “Profession” with the text:

Each Staff Member will have a Profession, tracked in the GDNT.  The default for Profession for all Staff Members will be Gopher, with the exception of the Writer, whose profession will always be Writer. As a weekly action a Staff Member may change their position to any of the below positions as long as the meet the requirments for that position.

Create a subrule of Profession “Writer” with the text:

Only the Writer may hold this position.

Create a subrule of Profession “Gopher” with the text:

Any Staff Member may hold this position, as it has no requirements.

Obviously we can create new proffessions, give them abilities and requirements, etc.