It wouldn’t be too difficult(tm) to fork their kernel and make custom configs of it. Here’s the git repo that holds their rpms and their respective kernel configs, it’s just that nobody has cared enough to create/propose “slimmed down” specialized kernel images: https://src.fedoraproject.org/rpms/kernel/tree/rawhide You can just clone the repo and point COPR to it, then automatically build custom kernels.

Awhile ago there was a proposal to move the x86 microarchitecture level. Here’s recent discussion on that proposal: https://discussion.fedoraproject.org/t/what-happened-to-bumping-the-minimum-supported-architecture-from-x86-64-to-x86-64-v2/96787/2

In general, though, Fedora would not want to leave any users behind. Instead, the proposal for hwcaps is currently being drafted: https://pagure.io/fesco/issue/3151 With hwcaps, default installs will be x86_64 v1, but will be upgraded to “optimized” packages if available upon updating. This makes packaging a bit awkward, though. Packagers already need to maintain packages for multiple versions of the distro. In fact, they need to support F38, F39, F40, and rawhide atm. Needing to maintain an extra 3 builds for each package on top of x86, x64, aarch64, ppc64le, and s390x is a bit of a burden, so success might be limited.

Distrobox, while feature-rich, is still a bit hacky (though it’s still more reliable in my experience than toolbx). You’re not the first to want this, though: https://github.com/fedora-silverblue/issue-tracker/issues/440