Basing this on Fedora doesn’t make sense. It tells me the private individual behind this proposal hasn’t done an extensive analysis on this.
Under what means? The target is public sector and the OS to replace (Windows 10, Windows 11) would be a relatively compatible release target. Fedora is a competent leading edge (Wayland, Pipewire, BTRFS) distro that runs as a 6 month point release. I wouldn’t see many reasons to not go with Fedora Workstation as a base unless going for an immutable base or a different core distro (OpenSUSE or Debian mainly).
EDIT: Missed that this is going to be immutabe, so it is likely being based on Fedora Kinoite, meaning there really aren’t many alternatives besides OpenSUSE’s offerings.
Why wouldn’t they use Fedora? Last time I checked they are paving the way from a security and quality perspective. The Fedora team does excellent work.
If you want “everyone” on board I’d take Mint. It just works and, for what I know, has no specific bad side effects.