Kindly consider adding R3 PgUp and R4 PgDn to the base kit, as well as using “Scroll” and “Num” legends instead of “Scroll↵Lock” and “Num↵Lock” (also “Caps” instead of “Caps↵Lock” on the stepped key) for a clean, single-line look across the entire set. :)
Further, I don't think a 1.25u Menu key is all that useful — consider removing it and just using the 1.25u Fn in its place? I believe that's what most recent GMK sets have been doing.
Also, those color comparison pics are super useful; thanks for those!