Really nice kitting, good job.
Consider adding a 2u Shift and numpad 00 to the extension kit; those are the only keys that are notably missing.
A generic R4 1u key (e.g. Code or Photo) would also be nice to have in that kit. I would change the extra 1u Ctrl to be that generic key, since there are no modern non-40% layouts that use 2× 1u Ctrl.
I suggest making the 1.25c, 2c, 2.25c, 2.75c keys in the spacebars kit alpha-colored instead of accent-colored. You could, optionally, also add 1c and 2× 3c keys.