Step 1-Pick a character with an article either in their fitcharacter00.pac or their motionetc so it doesn't shoot the filesize through the roof on your fitcharacter.pac where you'll be PSAing.
Step 2-Find your model for your character and rig it onto the character's bones (ie: War is rigged to Ike's bones so Chaos Form was also rigged to Ike's bones)
Step 3-Make sure your visibility bones are usable on both models, if you don't know how to do this it's under Objects/Polygons depending on what version of BB you're using but search KCMM and there's a guide.
Step 4-Make your animation for your character lets say I make it for Ike and then omit the frames where you think you'll have your transformation occur. Set the visibility bones to "set" for the frames you want the character there and "cleared" for when you want the main character's model to not be there.
Step 5-Export the animation
Step 6-Open the animation for your "transformed" model and edit the "omitted frames" accordingly (it doesn't matter if it messes up the other frames since the model won't be there). Then perform the same operation with visibility bones only INVERTED so the frames that were "set" for the original model should be "cleared" for the transformed model and the frames that were "cleared" for the original should be "set" for the transformed model.
Step 7-Both animations should be the same frame length so in PSA you can go to the subaction you want to edit and simply put:
-Generate Article: #
-Set Anchored Article Action:
-Parameter 1: Article #
-Parameter 2: AnimationData #
-Parameter 3: True (set this parameter to "boolean")
For information on the above code see here:
Step 8-Test in game and see if it works, if it doesn't you did something wrong
Proof-of-Concept:
Note: I chose not to write this tutorial before because I DO NOT want to answer a [censored]ton of questions on visibility bones and such techniques, if you have a question RESEARCH IT and if you still have one RESEARCH SOME MORE
then if you still have a question PM SOMEBODY ELSE but then if you're still confused I'll help you
-Omni