We need to export one or more projects regularily but currently the only possible way seems to be to do a full export, then export only the wanted projects into a clean instance and then to do a full export of the new instance.
This is too cumbersome to be feasible since it requires manual creation of workflows & custom fields which we use quite heavily.
Also there are already quite a few requests which are marked as duplicates of
JRA-1604 which is marked as 'Resolved' which is wrong since it is not resolved (as in that functionality is not available up to 6.0.2).
Please either reopen the linked issue or track that functionality here.