Model swapping characters

[Overly Epux]

I want to swap Shadow Plus (Sonic) with Olimar, Since nobody uses him over here, and I needed a way to add in shadow.  I'm not changing anything myself here I just want to know how the model/animations can be swapped.

And yes I did use the search function I couldn't find anything else on the subject.

[Canon98]

I dont believe the actual Shadow assist trophy model can be swapped with any of the characters so far. I think it's due to his minimal bone limitations, which none of the playable characters can support as of now. 

Though someone has animation swapped to 'fix' Sonics quills to look like Shadows.

[Overly Epux]

http://forums.kc-mm.com/index.php?topic=4777.15
That?  I'm trying to take Olimar and take out his model, and make him into Shadow+