Okay. So allow an "Improved Balthazar" mod that improves Balthazar in the FIRST fight against him - in his monastery. This does not change his dialogue, it merely changes his powers and his ability to use them, and possibly the powers of his friends.
And have the "Ascension" component mod, in which you face all the Five at once, in their "improved" versions, in the grand final battle. If you have installed this and NOT Improved Balthazar, you face Normal Balthazar in his monastery (either to fight with him or talk him into not fighting or into joining you), but Improved Balthazar in Ascension finale (on your side, or on Melissan's.)
And while you're at it, let's hear it for the option to face an Improved Sendai in her lair...
Jonathan.