UPDATE:
It's weird...I was able to replace only the head and the PSX did it however I still haven't got my model running on a physical device. I hoped that the fact that I made KERNEL.BIN assign the same weapon model to 2 weapons was the clue but it ain't. Next thought was that KERNEL.BIN slot 16 may be buggy because of the custom animation related to the loss of HP but fixing that neither helped.
Still I believe that the first Statement of Jeet wasn't as unrelated as I assumed at first because playing with the weapons section I got even epsxe crashing and it's 100% the same crash as on psx so I must apologise, the key lies within the weapons after all I suppose.
The crashes were most weird, here's what I've found:
- loading the weapon from model slot 16 crashes no matter what it is. I assumed it was due to the fact that this weapon is Ultimate weapon which has a custom animation but this is not confirmed yet. I must assign any other weapon to model ID 0F and see if the model loads then
- putting any weapon except the Masamune in slot 16 makes the game only crash when that slot is loaded because the related weapon is equipped. If masamune is in slot 16 it always crashes which is totally beyond me as the model is smaller than other weapons that Cloud has so it is not an issue of filesize
- putting a blank in slot 16(header+00) allows loading slot 16 after all but of course it is invisible. Still it is interesting that it works that way because it proves that it is possible to load a 16th weapon with my model even if it is blank. it is thus a problem with the models not with the principal of loading one. As all of this is just epsxe I still dont wanna count out UW's HP animation to be related
- loading the Masamune in more than one slot to get 2 different versions works as long as slot 16 is not involved
Putting all this together it is...unlogical. My final test to get around all points was assigning just weapons 1-15, replacing Buster sword and ragnarok with masamune model and putting slot 16 a blank and reverting the kernel to load an individual model for each weapon. Still PSX crashes...It's hopeless