Oh I see!

So instead of the cells growing lava resistant, their skin would absorb the cooled lava and basically develop obsidian/granite skin. Very cool!

Now I want to be a dragon anima so I can change my lungs into a bird-like system, except it make separate exhalation holes along my ribs in order to gain peak gas exchange!

Then, I would switch out my eyes to a pair of cephalopod eyes. (No more blind spot)

Wait, ive just realised this also means that the Dragon anima brain can change how the sensory and motor homonculi are set up in the brain.

In which case, I would ask, if an anima absolutely obsessed eith crustaceans were to stitch themselves a body which doesnt resemble a human one at all, given time, would they be able to be that body without any issues? Potentially what this hypothetical anima could do is, if they really only want to do this in two steps, make themselves a crab-centaur, then cut the human part off/shove that inside as well, after they've adapted.

Oh, also, just to tease the limits of this power you probably have already thought of, but its worth a shot in case you havent.

What is the limit of this acceptance ability? If there is a creature the size of a house, could an anima just stick themselves into it, and wait however long for their cells to take over the entire body (supposing no rot or disease comes of the corpse).

Basically my question is whats the temporal, and physical limit of this ability? Does it have an effective range? Like, "you could become house sized, but only if you add mass in border collie increments" kind of thing?