I have to be honest and say that ISO is not quite yet figured out. It's separate from the base kit for two reasons:
- Base is icon+text and ISO is icon only (as is historically)
- ISO sales are usually disproportionately low; why force everyone to buy it?
I know CandyKeys wants a NorDe kit, so it (ISO) may very well end up in the international kit.
While I get the reasoning behind not including ISO Enter in base because it's icon-only (I think that's pretty smart), you also have to keep in mind that “forcing” 4 keys in the base kit has a much smaller relative impact on pricing than the current setup (in other words, the larger the kit, the smaller the price per key).
Whereas putting the 4 ISO keys in base would result in a $2 increase to the kit's price (number taken from actual GMK quotes where I did this for a similarly sized base kit), the current setup forces ISO users to also purchase $40–$50 worth of icon mods to get the keys that they
need to be able to use their boards. In other words, you are effectively discouraging most ISO users from buying the set at all.
(Disclaimer: I'm not an ISO user, I just like to see kiting done in a sensible and considerate manner.)
Side note: The same logic could be applied to the R1 End, PgDn keys, which are only used by numpad users, and numpad kits also sell fairly poorly (see Dvorcol's numpad take rate stats for GMK sets). So they shouldn't be forced on everyone either, if you want to look at it that way.
Anyway, your idea of putting the 4 basic ISO keys in a NorDe kit is slightly better, but still isn't great for pretty much the same reasons as above. Namely, most ISO users are happy with basic support and don't want to spend a lot of money to buy an intl compatibility kit. This is why you always see these kits sell poorly. Rest assured that there are many more ISO users than sales of these kits would suggest.
BTW: icon mods: OG or centered? Some people will care to know... a lot.
What's better?
For what it's worth, I think IBM ThinkPads always used vertically centered icons for their icon-only keys, whereas some models under Lenovo went with the top-left (OG) approach.