I am not sure I would go for derived works here as much as trademark stuff. Far better option from where I sit, doubly so as you could probably sell any judge on "shucks your honor, we are just a small family friendly company trying to make our way in the world, this is likely to cause confusion in customers".
You expect a Streisand effect from this? I imagine some will try, storm in a teacup would probably be an accurate description of the end result there.
I will be impressed if this really makes it outside their echo chamber, at least beyond "in amusing news Nintendo is taking down porn based on their works, let us laugh the perverts". Or if you prefer what happened when Nintendo went toe to toe with the concept of let's play? Something you could arguably sell someone on. Result. Nintendo makes an awful contract (though one they legally are allowed to plump for) and nobody really cares, some of the moves probably will come up in game industy law trivia in years to come but that is about as far as it goes.
