Regarding the mentioned use case the approach i would suggest is create a framework application that will have the base rules and create implementation that will extend the framework application for each division specific rules.
Regarding 'setting up the operators to follow different pattern inheritance path' ,correct me if understood wrong if you are talking about separating the application for operators then you can reference the access group created for division specific application(Implementation) and for routing you can update the organization structure on the work tab of operator ID.
Just so I am clear with your approach, what you are suggesting is to create a Framework say Org-TestFW and create my case and business rules in here.
Then create two Implementation applications for each of my divisions. Example below
Implementation One: Org-UK-TestUK-Work
Implementation Two: Org-US-TestUS-Work
Then build Implementation one and two on top of TestFW. You understood correctly regarding the operators and I was thinking of this above approach by using the access group for each application to solve the pattern inheritance issue.
This approach seems to be the only option, but I was trying to get another perspective so that I would not have to create two separate implementation layers with rulesets using the above example TestUS & TestUK that won’t be used. I thought there would be a feature in Pega when creating an application to just extend the division layer and use the same implementation application.
If anyone else has a suggestion please let me know.