does it work is I example use a original Brawlmodel, export it to 3DS Max, do your step but import the vertex into the original brawlmodel in brawlbox?
It should do it, but I can try and see if it works or if something similar would work.
Edit: The brawl model explodes when I try that, because of the imported vertices differences compared to the brawl vertices or perhaps the object can cause it. I can try and replace the object and see how that goes.
Edit2: Okay, I managed to somewhat make it possible to make a custom shp0 animation on a original brawl model, but it requires object importing.
It even works in game, but it's still very weird, because I still get this...
Which is some of Ike's neck vertices "exploding"...
I think it's caused because SHP0 can't handle the Skin modifier with two bones connected (NeckN + HeadN). The three vertices are used by the NeckN bone.
So to answer the question ...
You'll have to either export the original brawl model whole from 3DS Max and replace all the materials, shaders etc. or be prepared to go through lots messy object editing or you'll have to edit the vertex in Brawlbox itself. Unless someone knows how to export the vertices to match the original's model.