Long ago, I botched a mobo BIOS update (Abit BH6), and for the reasons you mentioned/my incompetence, couldn't do another write through the floppy method.
Sold it on eBay (disclosed as such).
Later sent a message to the buyer asking if/how they fixed it. They shared that they did: with a similar mobo, booted the good one up, hot-swapped the EEPROMs and then ran the BIOS update on the bad chip.
I managed to do that once after flashing the BIOS for the wrong board, back when the EEPROMs were in DIP sockets.
Another time I was less lucky and broke an edge off the CPU die while installing the heat sink. This was during the time when the CPUs had exposed silicon with no metal lid. Instant dead CPU, expensive mistake for a college kid.
Sold it on eBay (disclosed as such).
Later sent a message to the buyer asking if/how they fixed it. They shared that they did: with a similar mobo, booted the good one up, hot-swapped the EEPROMs and then ran the BIOS update on the bad chip.
Smart.