Sounds highly doubtful to me!

Apart from the practical considerations already mentioned by Benjamin DAMET, the processor will be expecting to be writing to just a single chip, and will be using the command sequences for that chip. So you would also have to add something (a processor? a CPLD/FPGA?) to detect the command sequences, identify if the sequence applies to the "patched" area, and convert the sequence for your "patch" chip.

By the time you've done that, you probably might just as well have bought a new phone - never mind just replace the Flash!