A ROM hack that just changes his texture would work, or having a separate T-stanced low-quality Sora on the field that the Limit Sora could steal the texture from via RAM.
It's been a while since I've posted any of my creations here, but this seems like a good one:
Ultimate Master Form ~ Stylish Prowess:
Instructions and Codes
Code:
Step 1: Go to the World Map and activate the following code:
11CE0B68 00000057
1032E020 000001EA
1032EECC 000001E0
21C6C93E 000000FF
1032e0a4 000081A6
1032e0a6 000081A6
1032e0dc 000081A6
1032e096 000081A6
Step 2: Land the Gummi Ship in the Gummi Hangar.
Step 3: Activate the following code once the map has loaded:
20b18318 00ae1000
20a4e5b8 00a51700
20a4e4d8 00b5d550
20b6d8a4 ffff0000
20b6d8d0 00000000
20b0d8d8 00ad1b20
20bc2598 00bc8230
20ad7908 00a6d450
20ad7918 00a72560
20af0d60 00190003
20afe8d0 00210003
20b0d890 00300003
20c13128 00c0c620
20c13138 00c0e090
20bf6db8 00c13110
20bf6d78 00c13110
20bac578 00bc8200
20bf6d38 00c18040
20b6d8ac 0000ffff
20baf728 00bcaed0
20bf6c58 00c13110
20bac5b8 00baf700
20bac538 00bcc8a0
20a90c44 ffff0002
20a90c5c 0001002a
20bac6b8 00bc8200
20baf258 00bc8200
20bf9a58 00c13110
20a51258 00b466d0
20bac4d8 00baf700
20bf6cd8 00c13110
20c0c608 00c13140
20c0c618 00c16320
20baf6f8 00bc8200
20bf9ef8 00c13110
20bace78 00bc8200
20bf7678 00c13110
OPTIONAL: Change your keyblades with these codes and not the menu by applying them
after step 3:
Master Form Right Keyblade
11CD43BC 0000???? - Replace with UCM from Universal Character Modifier list
Master Form Left Keyblade
11CD439C 0000???? - Replace with UCM from Universal Character Modifier list
Step 4: DISABLE the step 3 code, enable the optionals if you'd like, and then walk
into the next room (do not access the World Map).
Step 5: Enjoy! You can now access the World Map again.
Warnings
1. If you are going to a boss fight, use a room mod code to instantly warp to the fight instead of the cutscene. Otherwise, you will lose keyblade modifications.
2. This will work in worlds with model changes, but you will have to access Master Form from the Drive menu. However, upon reverting, the game will no longer load Master Form's modified moveset.
3. In worlds with model changes, your keyblades will be changed back to Rumbling Rose and Star Seeker.
4. Before you land in the Gummi Hangar, you MUST have Donald and Goofy as your party members.
5. When you leave the Gummi Hangar, do NOT return to it. This will mess up parts of the moveset modification.
6. This will not work on patched ISOs.
7. Do not attempt to change your keyblades via the menu. All other things you can perform in the menu are stable.
Off the top of my head, there are three things that could be causing your problem.
1: You made those moveset modifications, then reloaded the battle with a mob added or removed that wasn't before (ex: You made a file dump, created a moveset mod, then decided afterwards that you wanted to remove Donald). If this is the case, scrap everything you did and redo your file dump when you are sure your conditions are perfectly set up. Conditions include role mods (ex: changing a mob to a partner/enemy/neutral role) and what mobs are loaded into the battlefield.
2. Saix is a special boss in that he spawns extra mobs, since his claymores that give you a Reaction Command are actually treated as boss roles. If you made this file dump after he threw out a claymore, it could have possibly interfered. If this is the case, scrap what you did and make the file dump as soon as he starts attacking, but before he lets go of a claymore.
3. You put something into your data that was an incorrect value (ex: maybe you accidentally made 56B's animation = 56C's effect, or you made 56B's animation = 56C). I suggest a bit of trial and error where you remove one line at a time (keep it saved in a text document or whatever you use to store data) and see if a crash still occurs. If this doesn't work, only apply a single line of code from your moveset mod at a time as a continued form of testing. If that doesn't work, your problem is probably one of the previously mentioned things in this list.
Assemble a slot 1 UCM code using the "Universal Character Modifier" section of the front page. You can find the digits, on your own, using the link at the beginning of the section.