Ability for Fusion to Automate tracking of Retainer hours

I'm wondering if anyone has any suggestions on how to track retainer hours that are specific to user role that is assigned to a specific Portfolio.

Right now this is a manual process 
We have a custom field on a Portfiolio that we manually adjust based on the addition of new Freelancers

Ideally what we would want is – if we onboard a new freelance – say 200 hours – this would automatically update the specific Retainer based on the Portfolio the Freelancer is being assigned – to reflect the additional hours.

3 - Followup to this – is there a way to create a report:

Is there a way to automate tracking a business line’s retainer hours, and then create a combination chart to show against hours burned?