Key Steps for Designing an Integration Flow

During my analysis and study for designing an Integration flow for creating a BPEL or an ESB service.

Below are some of the key points to be kept in mind for designing a service.

1. The Service should be re-usable, and is compatible with the business
2. Performance of a service during its execution matters a lot, so performance should be kept in mind like if there is no complex logic implemented then if it is developed in ESB then it's much better
3. Use of activities should be like it should achieve best practices.
4. All the outage scenarios or the outage endpoint of a service should be kept in mind while designing a flow
5. Use of external adapters or applications only if these are necessary like if we can handle name value pairs in DVM's then why to use an external database..

These are some of the points and are of my thought process only, and will be furnished as per my daily learning process.

Suggestions are welcome.... :)