Long time ago there was an editing software made for King's Field I-III called Sword of Moonlight, and later there was King's Field IV - The Ancient City. I see a lot of potential for a mod editing software made for the fourth game, the game still holds up due it's interesting atmosphere & monsters.
Also the graphical sets used (dungeons, fields, etc) are basic enough where I think it can be used for modding purposes if someone wanted to make a new dungeon or expand one. Also as a benefit if someone were to do this that they'll do the community a favor, and fix the emulation issues with the game (Black Pits of Doom) & any other errors.
Another thing...I'm curious to see if that game had unused content, it would be great to have it documented in TCRF.