Policy buiding for multiple VS's

Yes. The policy rules still apply. The only danger is that the app has changed in the interim, or there are other settings (profiles, iRules, etc.) on the new VS which would make the interaction between clients and the VS different. What you are describing however is actually a recommended approach to automatic policy building: Start with safe traffic, from a trusted IP address--meaning a source that you know, which does not and will not send bad traffic. If ASM builds the policy using known, good traffic, and you know the application is stable, then that "good" policy can be placed into production.