Here's a suggestion: Put the 1.5u Tab key in the Alphas kit (and remove it from Base Mods & Ergo kits) and put an Esc and a Return key in the normal mod colors in the Exotic kit. Why? Because this has several nice benefits: This would make the Exotic kit a _standalone HHKB Mod kit_!! Which would dramatically decrease the cost of getting this set for an HHKB layout without inconveniencing anyone else. Similarly, someone who wants to outfit two keyboards with different layouts with this set has a high chance of only needing one each of the Base Mods and the Exotic kits, since each mod kit would provide Esc and Return keys and the Tab would be provided by the Alphas, which one naturally would have to buy twice. Lastly, the Exotic kit would not only serve as extra mods for exotic layouts and a standalone mod kit for HHKB, but also as a de-accent kit (due to including non-accented Esc and Return) which are often very popular. Alternatively, the Esc and Return keys in the Exotic kit could have the mods base color but a different legend color, like red (my preference I think) or white, so that they're still accents, just more subtle ones.
What do you think?
Edit: Now that I think about it, the accented 1u Esc key might as well be in the Alphas kit as well. You never need more Esc keys than you need Qs, Ws etc and it's in just about every mod kit.
Another Edit: Thinking about the Exotic kit a bit more, I think I would prefer it if Fn and Ctrl keys of size 1.5 or higher said "Function" and "Control" instead. The 1.25 Fn key could also say "Func" imo.