I'm not sure this will ever be a thing; I mean I've seen some alice-layout boards with ISO support, and I know there is the Virgo, but here it would ask a redesign of the right part of the top case for only a couple of ISO users (I was an ISO user but let's face it, we are a really small minority).
I totally agree with you about ISO users, we are indeed a very small minority
But... if we can't ever have a chance... nothing will ever change. If I'm right, this project is still nearing completion, so why not make our voices heard? It would be nice to have a form to poll ISO interest for this forum - there really isn't much of a choice today, I hope the ISO lovers will make themselves heard!
Absolutely no harm in doing so, but I've also learn to not hope for ISO things to happen. In this particular case (pun intended), you would have to rework the border next to the pipe key to allow for the ISO Return key to fit which would mean either having no bezel there or shifting the entire TKL cluster to the right to allow for some space between the return key and the cluster.
While doable, for sure, this means Fox lab needs to design two top cases because that new design won't work for ANSI users (majority) and also means the ISO parts will be (much) more expensive and Fox lab will need to spend considerably more time during QC and, potentially, working with the factory if there is an issue with the ISO case (since you can't just order X more as a backup in case of issues and sell them later, without being sure they will sell).
In the end, it's always the same debate of "is it worth it for the designer/manufacturer" (yes, I hate myself for being the devil's advocate).