If you've ever had a message like:
Bluetooth: hci0: Failed to load intel firmware file ibt-20-1-3.sfi (-2)
displayed during the boot process (particularly if you have a LUKS partition and with mkinitcpio-bluetooth configured) this might solve the problem.
When the AX200 bluetooth device would encounter a problem (typically occurring during sleep/wake or hard resets) and (presumably) would need to have it's driver reloaded, the initramfs image would be unable to load it and you'd be left having to type a password for LUKS in using the integrated keyboard.
The solution is extremely simple (and documented in the mkinitcpio-bluetooth README), make the driver files available in the initramfs:
/etc/mkinitcpio.conf
or where-ever you keep mkinitcpio configuration:
# FILES
# This setting is similar to BINARIES above, however, files are added
# as-is and are not parsed in any way. This is useful for config files.
FILES=(/usr/lib/firmware/intel/ibt-20-1-3.sfi.xz /usr/lib/firmware/intel/ibt-20-1-3.ddc.xz)
# assuming your firmware files are xz compressed
It should now be able to load or recover the bluetooth device on startup automatically.