I used to know some Japanese collectors and they mentioned to me that te toy companies actually tolerate custom works as it helps to 'promote' the product. That's why in Japan there's fan written mangas of sorts. I don't know if they're applicable in this case.

If I recal, a few years back a Japanese fan was arrested for selling a custom S.I.C Kamen Rider figure. It was big news because it was probably the first time such a thing happened.

SMOG - thanks once again for your posting. Very interesting and an enriching post, one which helps me understand how this toy industry is run.  

 

I remember this story, he wasnt selling them he was just making them for his personal collection and was arrested for it