Not a bad idea, although I think it'd also require changes to how selection/d&d is handled, since if you even try to drag a file from the same lister to the metapane, the metapane switches to showing that file as soon as you click on it.
Well, I was about to open an issue, because I kind of expected this to work.
Please don't beat me, I just did. o)
But it seems dragging an image from the lister into the metadata pane (still) does not work, hu?
So I wanted to let you know, there is one more person interested in this, thank you! o)