I don't think a scenario reset will work for us as we definitely want to keep most of our Actual data, just for one example. We want to selectively purge one year of data across every scenario, not purge one scenario absolutely.
I did consider making a "storage" scenario that would hold a backup of a scenario so I could reset the original scenario, then import all but the oldest year of data from the copy, then reset the copy itself. However, that loses a lot of other audit data, drillback info, stage data, etc. that we'd rather keep for those years that are still recent enough to retain.