Use materials. Go into Materials1 and change the Type on Mant04, MantUra and mant2 to 3. The cape will still be there in BrawlBox but it'll be gone in-game.
Model imports take a lot of time and effort and usually end up very glitchy and broken so I don't think anyone will want to do this. It could be done if their were Raichu and Pichu vertex hacks made from Pikachu but no-one has made those yet.
It is possible because Ann Harvest's Mustacheless Mario was hexed and his moustache is on the same polygon as his arms and feet but I don't know how. You could remove it by vertex editing then push it inside the body so the tiny bit that is left won't be seen.
I just tried and it failed like .obj import does everytime. I've tried to import many different .obj models and never gotten one to work. There might be a wii game that uses mdl0s with an elephant on it though.