Nice! One step forward on a successful porting attempt has been done. There are things still needs to be done afterwards to make a clean-tidy-zero-bug porting attempt; but with trial-and-error, it wouldn't be that far.
Yeah, it seems Atton is rather a special-case. I have just experiencing some newfound things on his model; at least in my personal modding experience.
Anyway, you can save your time- if you like. Here's an ultra-dirty-work of my attempt porting his model. The body model will replace the default Scoundrel model [PMBBS] and the head model will replace PMHC05 [you could rename the texture/model to anything that fits your liking]: K1_Atton_as_Scoundrel.7z
I haven't include the DS transition and all his portrait. I believe you can do it yourself, and it is good for practice! Lol.
Enjoy!
Edit: You will witness the odds from his mouth and teeth. I have no idea to fix that; more experienced and skillful Masters will need to chime in to solve the matter.