Oblotzky has been discussing this - Space Cadet is the official name - in a Geekhack [IC]. It looks as if he has been in talks with GMK and Massdrop recently, too. Has this poll moved near the top of Massdrop's list because a drop might be on the way later this year? With doubleshot keycaps? I hope so...
https://geekhack.org/index.php?topic=94003.500#msg2622772
I second @BobtheSpaceCadet's concern regarding inverse dye sub. I know it has been done, but I'm not sure how successful it was. How about MT3 for sculpted profile - would that supplier be willing to do inverse dye sub?
Nice idea, but unless you're able to get inverse dye-subbed legends done as shown here https://geekhack.org/index.php?topic=82848.0 this set won't work. Have you contacted anyone yet to see if they can actually do this set for you? My understanding is that inverse dye-subbing isn't very common, but I'd definitely be interested in XDA if the dye quality is alright and if there's num row, F row, and blank singles available.