Extending Capabilities of the service_availability table

[kalaputi]

Hello all,

We are in need of extending the capabilities of the "service_availability" related table in a service offering that are beyond OOTB functionalities.

1. In a service offering, in the related tables under "Service Availability" table, there are multiple types enlisted (daily, weekly, monthly, annually, last 7 days, last 30 days and last 12 months). (see screenshot_1)

We have a need of covering the option for "quarterly". What is the best way to achieve this?

2. In the same "Service Availability" table there is a field "Total Availability" and this is where the downtimes of type "Outage" are calculated according to the agreed availability.
We also have a need to see not only this value, but the "Total Availability" value that contains the downtimes of type "External" as well.

So what we need is another value that has the downtimes calculated of both type "Outage" and type "External". (see screenshot_2) 

Is there a way to achieve this efficiently? 

Thank you