Yeah, I contacted WASD about it and this was their response:
We are unable to do any backlit keys and unfortunately, do not have any plans to produce them due to a limitation in the marking process. Backlit keys should be coated with a protective layer after they are lasered to make them durable. We do not have the equipment to perform that last step.
Please let me know if there is anything else I can help with. Thank you.
Though I did stumble upon the TG3 keyboard N8N was talking about (not the Deck Legend) in another thread, and then found I can buy one on ebay for $100 including postage to Australia (says they're new even).
Looks like the keys themselves are the same type as the Deck, but with a different font (Arial or similar, instead of whatever Deck uses, maybe Papyrus or something)
Which kinda makes sense, since Deck is a subsidiary of TG3.
I may decide to get the custom keycaps from Signature Plastics, even though they'll be expensive (near $300 for a 46 key set)
I wish the could do double shot with transparent legends though.
But my Ducky Shine's existing keycaps appear to be painted on transparent plastic anyway, the same way Signature Plastics does their backlit keys.