I don't think anyone would know without trying it and I don't think I've seen a single post on these forums, or any forum, about someone trying to Frankenstein a ducky chassis.
The bezel would have to be the same size to accommodate the keyboard, and it -seems- like the outside cutouts for the keyboard and numpad are the same size and width on both keyboards, so there would be a good chance.
As long as the outside keyboard bezel of a Legend would fit cleanly over the key layer of the Shine 5, then it would work, and all you would have to do is modify the underside.
Looking at the pictures of the Legend on the ducky website, most likely it will fit just fine. All of the ducky keyboards seem to use the same width dimensions for the distance between keys, mods and number pad.
I think you need to try it yourself and report back.
Most likely the outside MAY fit. The biggest problem you may have is the USB connector. However on the Ducky shine 3, it's a daughterboard attachment, not soldered on the main PCB, but rather a connector, so the orientation can be easily changed. So then you can just remove the connector and modify it to fit in the cutout for the legend.
