battle sprite corruption

is there any plan for a new level editor?

FF6LE is already a good editor that works and it is bug free (except one little bug that I know about if you enter an entrance of a map higher than 100). This bug does not corrupt the ROM and it's not what you were talking about. If something really bad to your eyes happens with the ROM, it'S most likely bad manipulation, from having opened FF3usME, a hex editor and FF6LE with the same ROM and clicking save here and there on the 3 tools to blanking by accident the event of the map or of a NPC like Nattak said. Either case it's not the editor that is buggy.

Also, there isn't much that demand for a better and new editor. The scene is a bit slow and those factors altogether does not motivate the people that have the will, passion, programming skills and FF3us knowledge to create what you expect would solve your problems. I could count these people on my hand(s) and without talking to them actively, I can imagine they have other priorities than a FF6LE Ultra.