I would like to discuss the following design aspect in detail.
//It is advised not to have same rule set in multiple applications// (this is one of the best practices pega is suggesting) ,if so consider an application say MyOrg-MyCountryDiv-MyAppSales-Work-Case1. This has a division layer MyCountryDiv and hence 2 rule sets MyOrgMyCountry and MyOrgMyCountryInt. Now if i create one more application ,say MyOrg-MyCountryDiv-MyAppService-Work-Case2 ; to reuse divisional rules ,I should include the 2 division rulesets ,isn't?. In this case both application MyAppSales and MyAppService is going to have same division rule sets isn't?. Is this conflicting the best practice.
Your divisional rulesets should be grouped into a new Rule-Application instance, and this new Application instance should be given as a Built-On application to your Implementation Layers MyAppSales and MyAppService.
This would fix the issue, and would adhere to Pega Best practices.