I'm a bit sad that there won't be a latin base kit.
That said I have a couple of questions about the alt alpha kit.
1, Have you considered adding in an extra tab key? These are often in alt alphas because that way you could cover two keyboards (one HHKB, one standard). It makes for a better value for your alt alpha kit in my opinion.
2, As far as I can tell you're doing UK iso both for JP basekit and latin alpha. However for the latin alphas you seem to be missing the '@ key and have a pipe key (which would be terminal ISO) instead.