>>> When Pega does a package install (or deployment, migration), it does 2 things: 1) Inserts new rule/data records 2) Updates existing rule/data records
One more thing I can think of that is done by the zip import screen is defining schema. For instance, if you create new class groups and migrate them, you can see this happening.
However, regarding your idea about using history records for restoration, I believe that kind of restoration is already available on a limited basis. For instance, if you delete a rule using the available UI on the ruleform, even if you delete the tab, you can go back to the "recents" list on the left margin of the developer portal to restore the rule. (wasn't there a way to restore rules even on older prpc versions even before that "recents" list existed on developer portal ?) /Eric