I'd love to see an alternative display mode where you can have two contact sheets open side by side at the same time. Much in the same way like dual pane file managers, with the ability to drag/drop and sync.
Sync should be based on chosen criteria relevant for photographers. For example it should be easier to send off JPGs to one disk and RAWs to another. Or separate edited pictures from unedited.
You can do that now. On Windows, drag the contact sheet tab down, and it will create a new column. On macOS, use File>New Window.