OJS's workflow is highly flexible.
The Copyediting stage can actually be restarted a few times, if memory serves.
What will happen is you'll lose all past records of the previous process.
If that doesn't fit your requirements, or if my memory has leaked, you may use the review process for the copyediting.
Using the review process will allow you greater control and further rounds to work with, with much better record keeping.
However, you'll need to register your "copyeditors" (translators, librarians for normalization, graphic artists, and other people you may need to involve) as reviewers, and find a way to "group" them with the reviewing interests so you can find them easily while searching and assigning.
I have filed requests to improve the copyediting stage, which is not used mostly, as it seems a very stiff process, but, since the review process can overcome most of the required needs, I doubt that changing the copyediting process or adding a customized workflow is in PKP's priorities right now.
Maybe creating groups of users, removing the "copyediting", layout and proofreading, and adding those to the "review" process would make OJS more flexible.