- Base Kit
Entails compatibility for most layouts: 60%,65% 80%, 100%
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Those R1 End, PgDn keys need to have the same legend color as the nav cluster keys in order for them to be usable on 1800/CP boards; otherwise, it's going to look garish. So, either make those two keys orange, or add additional R1 Insert, Delete, PgUp, Home keys with yellow legends.
I recommend changing the R4 Delete key to a more generic legend so that it's useful for more users and a wider range of layouts other than just GK64. For example, you're missing a red-legend Fn key on R4 (for 1u Fn on the bottom row). You're also missing an orange-legend Fn key on the same row (for right column setups).
To address both of those issues, I'd change the red R4 Delete to something like Super, and I'd turn the second R4 1u Ctrl into an orange Hyper key, since pretty much no modern keyboards outside of 40s use 2× 1u Ctrl. (Super and Hyper are just examples; you can use any generic-sounding legend that the manu has molds for.)
Speaking of 40s, I don't see the 40% kit anymore, so you can remove the second 1u spacekey from the spacebars kit.
For the sake of consistency, consider either changing the two-line Caps Lock legend on the stepped key to single-line Caps, or the single-line Num legend to two-line Num Lock. Seeing as you also have single-line Print and Scroll, the first option is probably better, if the manu has the mold for it.