Comparing multiple CS entries in rules extensions

I've created a lab scenario where I have many CS entries to one MV person. Each CS record has a date range specifying whether the information in that record is current, and a job role. Certain job roles out rank other job roles.  So a user may have three job roles: Cleaner, Designer and Manager. Manager outranks Designer, Designer outranks Cleaner. 

If I create a user with one record showing them as a Manager and another record showing them as a Cleaner, both with valid dates how can I make it so that the Manager record outranks their Cleaner status, yet if their Manager record expires first, the Cleaner status takes precedence?

I know that to achieve this I could import additional information into the MV or portal, or I could handle the information prior to presenting it to FIM but I am curious to know whether it is possible entirely in rules extensions.

In pseudo code, my process was:

Are CS attributes present? 
    Is the date range current?
        Is the start date newer than the existing start date?
            Does the CS-jobrole outrank MV-jobrole?

But then I realised if a user has previously been a Manager but is no longer, the job role will remain Manager as this outranks the jobrole CS entry.

Any suggestions? Am I missing something? Thanks.