natural shape limitations?

[Venger]

Okay, so, I was discussing with my brother that eventually a momf could take the shape of a wil o' the wisp for their kickass magic immunity and natural invisibility. he said that while great defensively, they "wouldn't be able to do anything" and I reminded him of the existence of natural spell. he said that since the example is an eagle waving its claw, that a will o wisp, lacking appendages and being a glowing light orb, would not be able to do anything. shifter's speech allows speech, so that's out of the way (despite natural spell specifying that you substitute noises of whatever you turn into) I assumed that the same extended to your somatic components (bobbing up and down for a will o wisp? it's kind of a unique instance. I can't think of anything else you can wild shape into without any limbs at all. even oozes have pseudopods) I asked if by that token of logic a shark or anaconda would be able to cast spells and he said a shark could "wiggle its fins"

I was somewhat at a loss after that, so I come to you. who's right? is there some answer I'm missing?

[Deophaun]

First, will-o-wisps can speak, so at the very least you could cast spells that only have verbal components. Second, the Natural Spell feat has no requirement that you have appendages to cast the spell. It simply says that you can cast spells with verbal and somatic components while in wild shape. Explaining how that happens is up to you and the DM, but by RAW it happens. As long as you are a will-o-wisp through wild shape, you are good. The feat that limits you to needing appropriate body parts is Surrogate Spellcasting in Savage Species.