You can still do this for boot code if the error isn't significant enough to make all of the boot fail. The "fixing it by plugging it in somewhere else" could then also be simple enough to the point of being fully automated.

ZFS has "copies=2", but iirc there are no filesystems with support for single disk erasure codes, which is a huge shame because these can be several orders of magnitude more robust compared to a simple copy for the same space.