Genji or Gauntlet specific weapons

To the question "Is it possible to <inset hacking idea here>" the answer in 95% of the time is yes.

In this case you need to add new propertie(s) to each weapon, move the data if you need to, change what is needed in C0, C1, C2 and C3 if you move the data and create a routine at the right place to check that new weapon property.

I have no clue how to achieve this in detail and it's beyond my hacking skill at the moment. Maybe you could ask the guys at Slick Productions, they have insane ASM knowledge and some of them have been working on the FF3us ROM for years.

Edit: A easier solution would be to create a table with one byte for each weapon and instead of moving the item/weapon data, make a check in that table when you need to. This solution still require good ASM knowledge and dissasemblies knowledge as well.