I should be able to export / import a Space's *history*

(User Story, Investigate , Priority: Medium, Test Status: No automated tests yet , Reported By Justin du Coeur, )
History, Import and Export
Summary: Currently, we only export / import a snapshot of the Space. But it would be even better to be able to export the full history, and recreate that.
The output format might be XML or binary.
The trickiest problem here might be Identities: we have to somehow recreate the History without necessarily having the same Identities present on the receiving system.