I'm one of the two ZFSBootMenu authors - it's great seeing people using it in the wild. I'm not sure if this is something you're doing already, but don't forge

I'm one of the two ZFSBootMenu authors - it's great seeing people using it in the wild. I'm not sure if this is something you're doing already, but don't forget that if you zfs send a snapshot to your storage pool, you can boot from that snapshot in a pinch. We also (this past week) added a modifier to zbm.prefer - !!. If you specify zbm.prefer=zroot!! on the KCL, it'll only import the zroot pool. This might help your boot times by skipping importing your 56 drive storage pool. We should have a new release out in the next few weeks, otherwise that feature is in the master branch if you build your own EFI executable.