Auxilliary & Relic Commands

I had an idea a while back for a modification of how the command relics work. I always found it annoying that older commands are overridden with new ones when using command relics.

I prefer to have the option to use the original command as well as the new one. For example, if I equip Edgar with Dragoon Boots I'd rather be able to keep Fight and have Jump appear in a secondary command window along with Def.

What I don't know is if the Def. command window is hard coded or if can be modified easily and can the relics be easily modified to add a command there instead of replacing an existing one?

EDIT:
Another thought that comes to mind is the possibility of having every character use a standard command set (Fight, Defend, Magic, Item) and having the special commands only appear on the Defend sub-menu.
Or another possibility is modding the main menu into a scrolling menu and simply allowing more than 4 commands.