Would it make sense to allow a Lister's "viewer" panel to have tabs?
Where the "default" tab was the current selection items viewer.
But additional tabs could be added that got notifications as the "selection changed" but could in fact display whatever they wanted? (scriptability also adds more dimensions to what is possible; allowing new panels to be scriptably added or managed for a listener. Ideally they would actually run in a separate process so they would-not impact DOpus if they had issues.)
That design would make it a good bit easier to do nice extensions like an editor, embedded web-view, or console-windows etc.
It is also worth looking at "how ConEmu can be embedded today"; and, if you're following Microsoft's work on PTY pseudo-consoles, SSH, and Linux, read this also.
Currently ConEmu works fine in Explorer, but it does not recognize the DOpus preview/window layout. So additional developer/usage advice is needed from DOpus team to do this right.