3.5″ floppies were a bit before my time but I still know them. I would be seriously concerned about data integrity and about some magnet flipping random bits. Sure, there are mechanism to detect such errors but there are always parts that could slip through. A checksum for your firmware binary blob doesn't help if the config file switched rudder and elevators. Very like unrealistic but I seriously would trust a cheap USB stick far more than a floppy.