Relatively straight-forward once you read up on alpm hooks [0] to make sure you're rebuilding the init at the right times. The wiki [1] has working examples that are drop-in dracut replacements for /usr/share/libalpm/scripts/mkinitcpio-{install,remove}. Dracut also makes it easy to build unified kernel images that can be signed for secure boot, which I never figured out how to do with mkinitcpio.
Is there a good reason for this? The last I read [0], Dave didn't think that mkinitcpio was the way forward. I've since migrated my setup to use dracut and haven't looked back. Is it just inertia that's kept mkinitcpio alive?
[0] https://man.archlinux.org/man/alpm-hooks.5
[1] https://wiki.archlinux.org/title/Dracut