This doesn’t solve your present problem but maybe it helps to avoid it in the future.
Instead of physical volumes, you could use thin provisioned logical volumes. LVM is the word here. These would allow you to maintain volume division without fixing the sizes rigidly.
Another way to do this would be to use a BTRFS filesystem, and it’s subvolumes as ‘real volumes’. The semantics would be the same.
Huh, I had no idea that tractors etc. were also facing this no-self-repair crap. Always though them to be something like the gold standard of repairability… but apparently it was just the old ones.