I mean I do keep them but they get too old eventually and then they won’t mount the pool, or will only mount it read-only.

Both ZFS updates and pacman breaking are rare enough that I forgot that would happen. Though using this rescue system would work, there's also a group that maintains a script to grab the correct ZFS module for a running archiso, might come in handy for you.

https://github.com/eoli3n/archiso-zfs