Finally, I had not talked about this in public nor was going to before reaching out to the asahi team. We've been talking about different to addressing this issue among Flatpak/runtime developers for a while and wanted to explore the different solutions once I had access to an asahi machine again.
Likewise you could have asked why shipping an extension as a distro package and using that flatpak-builder manifest is a dead end and how it would explode ;)