SRAM Expansion

Emulators and ROMs don't have hardware limitations like cartridges though. If you wanted to enlarge the SRAM 
for a ROM I believe it would be as simple as adjusting the ROM header byte at $C0/FFD8. The value for the 
original FF3 ROM is $03, which indicates a 64K Bit SRAM (8192 bytes). If you change this value to $05, the 
emulator should automatically increase the SRAM size to 256K.

It seems setting the byte to #$07 gives 128kb. Maybe 256kb would be #$0F, I'm not sure. As this post state, if your game has 8kb of SRAM, it would be mirrored among all the banks. A SRAM hack is also a good way to keep repros guys away, as I'm not sure if carts with 128kb or 256kb of SRAM are found easily.

Hooray! This is the first step towards many interesting possibilities such as expansion of spells, items, chests, event bits. Not to mention the incredible utility of having lots of free general-purpose RAM available for battle functions.

Yes! FF6-G and FF6 T-Edition use it for item expansion among other things like more rare items. We could even have a bestiary with each monster having a bit set to show his entry or more rages. There's a lot of possibilities.