The issue that I was facing here was not that disk hardware is unreliable, or that consumer disks fail.
Btrfs was compensating quite nicely for both the failure rate of the physical drives (by having raid1 level redundancy) and the errors introduced by USB weirdness, resets, and general unreliability (by checksumming all reads and relying on replicas when checksums failed).
I've said it already but I must stress that numerous physical drives had already failed in this filesystem already and the recovery process from that failure was as seamless as advertised.