I know the FKS model can only replace an existing weapon (but still keep the latter's moveset), so how about it? Is there a 360 method for doing this? Jappi's save editor doesn't seem to have a model replacement function or the FKS in the database. And hex editing is outside of what I can do (unless there's a specific editor for this that makes it easy).
So have at it; dat FKS looks too badass not to use~