What you're missing here, it appears to me, is that you assume that you can get the database in exclusive mode. If you can't get it exclusive, you can't close the source table. That is, you can't be sure that no one else is using it at the same time.
Also, you've complicated things by requiring an empty copy of the database. If you make structure changes to the database, you have to make identical changes to the production database and the empty copy (or copies). If these various versions get out of sync, you have a big problem.
My method is something like yours, except it is simpler because it does not require an identical empty copy of the database. It simply does the equivalent of a DOS copy of the entire database to a subdirectory on the local drive and then backs up from there.
This method still suffers from the possibility that the copy will be made at the same time some other user is executing an update; in this case, the database that is copied may not have integrity. But it is a chance we take and the price we pay for permitting back ups with users on the system. No way around this unless you use a client server back end such as SQL Server. Of course, the operator could always try to wait for a time when no one is on (after the end of the work day, for example).
Regards, Chaim