Personally, I would love to see glitter mods as a standalone kit, so R1 owners can use it as an expansion pack for their sets. This might also allow you to appease everyone who doesn't like glitter being the default choice in the base kit (although I dig it; it's FF2, after all, not FF R2).
As far as the kitting goes, as it currently stands, you can't fully cover a regular
1800/CP/96-key layout without using the R1 media keys from the base kit above the numpad. Which some users may want to do, but probably not everybody. The keys that are missing for a more common setup are white-legend R1 1u PgDn, End.
Consider replacing the second R4 1U Ctrl (which is seldom used on anything other than 40% ortho layouts) with a R4 1u Prev key, for another variant of the right column media keys setup. The R3 Next, R4 Prev keys could then also be used as a substitute for R3 PgUp, R4 PgDn for 65% layouts (these are currently missing from the kit).
Also, to mirror what other folks already said, F13 in base and white F1–F4 / F9–F12 keys in alphas.