I suggest you read a few articles on the wiki, there's plenty to find on Zimbra server migration, and I think there are easier ways to migrate then what you're suggesting in the topicstart. A good starting point:
Zimbra to Zimbra Server Migration - Zimbra :: Wiki
I would first move the ZCS 5.0.x install from server A to server B and then upgrade to ZCS 6. My advise is to upgrade to ZCS 6.0.6 instead of ZCS 6.0.2. If you use family mailboxes, definitely do not use any version prior to ZCS 6.0.5.