We need to have a view of an "approved" roadmap but also have the ability for various product managers to be able to use the tool to create alternative versions/proposals for the future.
This will allow product managers to move features across releases and quickly put together and pitch their ideas using the board. At the same time the "approved' roadmap remains intact for work to continue.
One potential workaround would be to leverage Notebooks in creating and tracking multiple variations of a roadmap.
You could add your "approved roadmap" to a notebook. For this roadmap, you can set the the "refresh" setting as "Use snapshot." This would take a static snapshot of the roadmap and allow various product managers to continue to work on the roadmap and make changes. They would also be able to save their variations to a notebook (with a snapshot view).
This would allow you to create and compare roadmap variations.