hmm. I'm trying to design a (read-only) 5.25" floppy disk that can survive damage to the visible disk surface.

Now you could obviously do things at the sector level with parity data, like treat it like multiple pie-slice drives in a RAID5 array.

but a dumb-but-should-still-work way to achieve this would be to just write sectors twice, 180° across from each other. If you ever fail to read a sector, just read it again. you'll get the other copy of the sector.