There's a couple of really weird exclusions here, like the top row pg dn and end keys, 1u numpad 0 key, and 1.5u alt and fn needed for a drop shift keyboard and other 1800/96% layouts.
It would really help broaden compatibility if there was support for the non-standard bottom row using 1.5 u ctrl and alt and 6u spacebar. There's not a lot of nice pbt backlit sets out there right now and adding that would give lots of people with other brands of gaming keyboard the opportunity to get a nice set.
Add in 1u ctrl, alt, and fn keys for the 65%, 75%, and 1800 boards that use them and you'd also make this set work for a lot more people.
I personally would really like to see pg up and pg dn in rows 2 and 3 respectively plus a row 4 end for the 65% right column that's common on non-drop boards. This isn't as important to me as the other things I mentioned but I think that is a much more commonly used layout if popular GMK sets are anything to go by. (row numbers assuming #1 is the number row and #4 is the shift row)
Sweet sets though, I'm very interested to see where you can take them and I think it's great we are getting good pbt backlit sets lately.
EDIT: Oh, also I think the kit image makes it a little tough to tell the row height of some of the keys. The 1.75u shift being shown next to enter is slightly misleading, but it took me quite a while to realize that the navigation keys shown above the numpad are for the alt right column and not for 1800 layouts.
SECOND EDIT: I also didn't realize that the drop shift uses a 1u + key on the numpad, so that is missing here as well as the proper row "-" key to accompany it.