The point is that there isn't one "identifier" for compatibility purposes and we don't want to create one. This isn't an nvidia situation where we will have ongoing versioning. So there is no single identifier that whoever wants to roll out the GL driver extensions would be able to use.
On top of that, putting Flatpak changes to autodetermine this stuff upstream or in official Fedora packages makes no sense, because the whole Remix is a Remix for exactly this reason and we keep the UAPI-related things in downstream COPRs for this reason. Therefore, the only option we'd have left is to fork and overlay Flatpak to add Asahi-specific logic in the Remix... and no, sorry, we aren't opening that can of worms, that's way worse than what we're doing now shipping host extensions. We're trying to *reduce* our forked packages, not add to them.
The current solution works for most users/cases, I fail to see how it's a "dead end", and it keeps our workload to a minimum (we just need to bump the Mesa tag name in two more places when we do releases). If and when it "explodes" we can talk about doing it another way.
How the extensions are packaged aside, if you do have a better approach to the actual Mesa build than flatpak-builder, we'd be happy to hear that. But we have no plans to change how we actually ship the extension packaged right now.