@MichaelChen

I'll throw one more option out there.  Lets say that you have multiple built-on apps that you want to leverage.  You can first do an import and mark all your assets (case types, data objects and persona's) as do not build.  After generating your app and reviewing and potentially cleaning up what was generated, you could merge, build your dev and test apps, set up your org app and then add your reusable apps to your implementation app.  Once that is done, you can do an extend with blueprint, using the same blueprint, but this time selecting a case type and its related data classes and setting up the inheritance at that point.

I just did an import this way last week: creating an empty app, doing all the set up stuff adding in component apps and then doing the next import (but doing it from the implementation app) and then moving the new branch to the dev app for review, cleanup and merge before we started refining the UI.