It looks like it can't be done. The dragged element is put into container that has it's own, lower than 1, opacity. This means that while you can lower the opacity of the dragged element you can't get it higher than the opacity of the encapsulating element.
It might be possible to override default browser settings for such element, but since nothing is added to DOM during the drag it would be very tricky at best.
与恶龙缠斗过久,自身亦成为恶龙；凝视深渊过久,深渊将回以凝视…
