Can any body suggest the way to oraganize and share rules for mutiple business lines with each having multiple apps

Basically I am looking at Business Rule management , development and deployment best practices across the organization taking into consideration all Business Units that needs Rule based apps.

option 1) Have one run time deployment (Expert engine) for all these apps with large memory.

option 2) Have one BRMS/Repository for all the rules in the enterprise across the business lines and then a sperate run-time for each app/business unit ?

If we assign a package for entire rules in a Business unit or BU_App can we have permissions around package so that certain project teams can work on those packages but not others.

Option 3) Should one team be responsible for all the rules in an enterprise ( across BUs ) and provide decision services to the corresponding apps in each BU ?

Any references on web is great!!