Multiple questions. I would like to know for a hackgame I want to do.

You can expand the ROM with FF3usME, which can be found in the Tools section on this site.

As far as creating a new menu-based command, it would probably be rather difficult as the menu-building routines aren't well documented, and probably not well understood (this method requires extensive ASM hacking). It's more doable if you were willing to hijack another menu-based command (like Lore or Tools, though the latter may restrict you to eight abilities).

You'd then have to find or make room in the spell list (again through FF3usME) for all the Sword Magic skills you wanted to implement, bearing in mind that keeping them consecutive makes populating your new menu much easier. If you're teaching the skills via level, you can use the existing level-based learning routines (for Celes' and Terra's natural magic) as a guideline for implementing your own. I haven't looked at it, but it may even be possible to use part of the existing routines for the sake of efficiency.

Either way would require quite a bit of ASM hacking and likely be a considerable time sink.

I had a similar Idea, in which the Item would change Runic into MagiSwd and then it would randomly cast 1 of 5 different elemental Physical Attacks.

This, on the other hand, would be much easier to pull off. Something similar was requested a while back dealing with Banon's Health command randomly casting one of the Cure spells, which could be easily modified to do what Cyprus suggested.

https://www.ff6hacking.com/forums/showth...p?tid=2439