I would suggest if it’s a large migration to just not use emcopy. There are other commercial options on the market that not only understand and handle it correctly by default, but also are far faster and easier to support.
My company, Datadobi for instance has file migration software that understands and even does prechecks on the source and target encoding, and stores all the logs properly in the correct language / Unicode.
If you want more information certainly drop me a line.
Principal SE, Datadobi