Seems sort of odd to keep PrtSc, Scroll, Pause as text when all of the other mods are icons, doesn't it? Perhaps you could do something similar to
KAT Hyperfuse for those icons?
Have you looked into making the Backspace and Enter arrows a tad smaller/narrower? At the moment, I find them to be overwhelmingly large compared to the other icons. I think a small change here would go a long way.
I think the trash can Delete icon looks a bit out of place next to the fairly abstract, less detailed icons on the other mads. Have you considered using a short, right-facing arrow similar to the Backspace one for Delete? Something like
⭢ or
▸.
Since the Super and Alt icons are quite abstract, perhaps there's no need to include the 1u ▲, 1.5u ▼ variation? Since practically either icon can stand for either key.
The R3 '@ UK key in the add-on kit needs to have a け sublegend rather than ふ because it's replacing the '"け key.
Speaking of sublegends, consider changing the R1 1u \|ー key in base to \|む, and adding a R1 1u `~ー key. This way, both JIS and regular ANSI split Backspace layouts will be covered (currently only JIS is covered).
Please consider including a 1.75u Fn key (with either
≡ or the “layers” icon) in the add-on kit.