The kernel has no idea about /lib (unless you're using the in-kernel firmware loader, which you really shouldn't be) - the rtdl path is present in every ELF object that depends on it, so the "kernel tweak" would be hacking the ELF loader to rewrite /lib (or /lib64) to something else.
The parent commenter is already suggesting "just run a regex", so it seems like a trivial extension to their simple solution to "just run patchelf on every binary on your system"
The in-kernel loader can't defer loading if, say, a module is loaded before the firmware is available. Instead it can be handled in userland - the kernel generates a request when it wants firmware, and the userland hotplug agent can satisfy that later
